List of Line of Duty episodes - Wikipedia List of Line of Duty episodes Line of Duty is a BBC police procedural television series created by Jed Mercurio starring Martin Compston and Vicky McClure as Steve Arnott and Kate Fleming ; detectives assigned to an elite anti-corruption unit designated AC - 12. The stories follow investigations into suspected corrupt police officers, at the behest of Superintendent Ted Hastings ( Adrian Dunbar ). They are Lennie James as DCI Tony Gates, Keeley Hawes as DI Lindsay Denton, Daniel Mays as Sergeant Danny Waldron and Thandie Newton as DCI Roseanne Huntley. Hawes reprises her second series role during series 3 and Craig Parkinson 's reprises his role as DS / DI Matthew ' Dot ' Cottan during both series 2 and 3. To date, 23 episodes have aired, with the first and fourth series linked thematically, and the second and third series similarly connected : however, all series have a single overarching connection, with all series referring to the same criminal network involved in the events of each series ' plot. Contents 1 Series overview 2 Episode list 2.1 Series 1 ( 2012 ) 2.2 Series 2 ( 2014 ) 2.3 Series 3 ( 2016 ) 2.4 Series 4 ( 2017 ) 2.5 Series 5 2.6 Series 6 3 References Series overview Series Episodes Originally aired Ave. UK viewers ( millions ) Series premiere Series finale 5 26 June 2012 24 July 2012 3.80 6 12 February 2014 19 March 2014 3.43 6 24 March 2016 28 April 2016 5.42 6 26 March 2017 30 April 2017 9.55 Episode list This section 's plot summaries may be too long or excessively detailed. Please help improve them by removing unnecessary details and making them more concise. ( March 2017 ) Series 1 ( 2012 ) The first series of Line of Duty, broadcast from 26 June 2012 and consisting of five episodes, follows DC Kate Fleming ( Vicky McClure ), DS Steve Arnott ( Martin Compston ) and Superintendent Ted Hastings ( Adrian Dunbar ) as they lead an investigation into the corrupt actions of DCI Tony Gates ( Lennie James ). The supporting characters include DC Nigel Morton ( Neil Morrissey ) and DS Matthew Cottan ( Craig Parkinson ). No. overall No. in series Title Directed by Original air date UK viewers ( million ) `` A Disastrous Affair '' David Caffrey 26 June 2012 ( 2012 - 06 - 26 ) 3.76 A counter-terrorist police raid kills an innocent man after mistakenly raiding the wrong flat. DS Steve Arnott refuses to take part in a cover - up. He is transferred to AC - 12, an anti-corruption squad led by Superintendent Ted Hastings. Hastings informs Arnott that his first investigation will focus on DCI Tony Gates, the senior officer of TO - 20, a unit of Central Police CID, who has just been made Officer of the Year. Hastings has received a tip - off that Gates has a suspiciously high clearance rate due to `` laddering '' -- a process in which a number of different charges are placed on the same defendant to increase an officer 's number of successful cases. Initially, Hastings interviews Gates on a minor charge -- failure to report accepting a free breakfast for apprehending a mugger outside a local cafe. Meanwhile, Gates offers advice to his lover, Jackie Laverty, after she claims to have hit a dog after drink driving on her way home from a work party. Gates initially offers to help her cover up the incident, by faking a break - in at her home. However, when DS Cottan informs him of the cases that have come in overnight during the morning briefing, he discovers that Jackie actually killed a person during the incident, and not a dog as she claimed. Gates urges her to come clean. Meanwhile, Kate Fleming, currently assigned to divisional CID, approaches Gates and asks if she can join his team. He suggests she come out for drinks with the team to see how they get along, unaware that she is secretly working for AC - 12. Meanwhile, DS Leah Janson informs Gates that crime statistics on the Bogg estate are on the rise once more, so Gates assigns TO - 20 to investigate. Surveillance reveals that two suspected drug dealers are operating out of a derelict house. Gates asks his team to take turns keeping an eye on the property. Laverty comes in to make a statement about the hit and run to an intelligence officer, but fails to disclose her part in the victim 's death. When the victim is identified, Gates manages to gain access to the computer records, and deletes the missing persons report which identifies the victim -- but not before Arnott manages to take a look. `` The Assault '' David Caffrey 3 July 2012 ( 2012 - 07 - 03 ) 3.84 Gates continues his investigation into the double murder of the two suspected drug dealers, and interviews a less than co-operative witness -- whom he forces to talk by threatening that, even if he does not talk, he will be labelled a police snitch. Dot and Deepak apologise for leaving the surveillance early. Meanwhile, Simon and Karen respond to a silent alarm at a block of flats and catch a burglar in the act. Leah interviews him, and during interrogation he also confesses to a number of other offences. Meanwhile, Arnott ponders why Gates has taken on the case of the hit and run. Whilst interviewing waitress Nadzia, she informs him that Gates ' breakfast companion was tall, slim and dark - haired, and Arnott suspects she may have been describing Laverty. A search on the police database reveals a number of burglaries committed by the offender caught by Simon and Karen were on properties owned by Laverty Holdings PLC. Arnott visits a hairdresser 's that was burgled and suspects that Laverty may be running a money laundering scam. Back at the murder scene, the team realise that the attackers can not have found what they were looking for, but upon discovery of a secret hiding place where they suspect the drugs may have been stashed, they find it has been emptied. Meanwhile, Gates confronts Laverty over the death of her accountant. She tells him that her plan was to expand her business and that he disagreed with the idea, but Gates realises that he discovered that she was laundering money and threatened to tell the police. Gates arrests her, but on the way to the police station she persuades him to release her. Meanwhile, another drug dealer is found dead on the estate, but Gates is nowhere to be found. Kate realises that Gates has disappeared and informs Arnott. Back at Laverty 's house, she and Gates engage in another passionate encounter, until masked intruders force their way in. Gates is knocked unconscious, Laverty is murdered, and the unconscious Gates 's fingerprints are placed on the murder weapon. `` In the Trap '' David Caffrey 10 July 2012 ( 2012 - 07 - 10 ) 3.80 Arnott speeds to Laverty 's house following a tip - off from Fleming, only to find Gates supposedly searching the property, claiming that he has come to arrest Laverty. Whilst at the property, Gates tampers with evidence, hiding his whisky glass and wiping his prints from the bottle just as his team arrives. Arnott demands that Forensics dust the table for prints in the hope of proving that Gates was at the property before Laverty disappeared. Hastings and Arnott haul Gates in for questioning. Gates confirms that Laverty was an old flame, but he denies all knowledge of the money laundering scam. Gates flounders when Arnott asks him how he managed to park his car on Laverty 's drive unless she let him onto the property, a hesitation which Arnott suspects is a sign of guilt. Hastings informs Gates ' senior officer that he is to be taken off the Laverty case. Fleming looks at CCTV from the night of the murder of the two drug dealers. She finds video footage which suggests that the killers circulated the area for some time in a car on false plates until Dot and Deepak left. Meanwhile, Gates tries to dispose of the whiskey glass from Laverty 's house. Fleming receives a call from uniform to say that the cloned car has been spotted, and Gates and Morton give chase. During the pursuit, Gates is kidnapped and taken to a warehouse where he is shown Jackie Laverty 's body and is told to stay quiet, or the knife with his fingerprints on will be handed in to the police. A dogged Arnott acts on a tip - off to say the whiskey glass is hidden in a storm drain -- a fact which Gates reveals he falsely told Deepak, supposedly confirming Deepak is the mole leaking information to AC - 12. Meanwhile, Arnott discovers his colleagues from the armed raid have accused him of messing up the orders, which resulted in the death of an innocent victim. Racked with guilt and his inability to see past his colleagues ' betrayal, Arnott sends a text to Fleming and Hastings reading `` I 'm no longer the man for the job. Gates has won. '' `` Terror '' Douglas Mackinnon 17 July 2012 ( 2012 - 07 - 17 ) 3.87 Fleming suggests to Arnott that the link between Laverty 's money laundering scam and Gates may be his children 's school fees. Arnott visits the school, who later confirm that Laverty paid the deposit and the first full term in cash. Arnott agrees to return to AC - 12. Meanwhile, Hastings decides to bring in the rest of Gates ' squad to interrogate them over the ' laddering ' charge. Morton refuses to comment, Fleming sticks to her cover and decides to back up Gates, but during questioning Hastings interrogates Cottan about the night of the surveillance on Greek Lane, and he claims that Gates ordered Deepak and him to end surveillance, unaware that this would create a prime slot in the timeline for the killers to strike. Meanwhile, forensic evidence at the crime scene and Arabic books belonging to the victims leads Gates to cook up a story regarding a possible terrorism plot, allowing him to wind up Arnott about the armed raid in which he failed to capture a terrorist cell. Meanwhile, Gates tries to find the location where Jackie Laverty 's body is being kept. He receives another call from ' Tommy ', who informs him that Arnott has been poking his nose into Laverty 's businesses, causing him to lose profits. ' Tommy ' informs Gates that he wants Arnott out of the way. Hastings and Arnott inform Hilton that they have a witness who claims that Gates controlled the sequence of events to allow the murder of the two drug dealers. Gates finds the location where he was held, but Laverty 's body has disappeared. Morton catches Fleming with two phones and realises she was the real AC - 12 mole. He assaults her and drives off to find Gates. Arnott receives a phone call from the owner of the hairdresser 's claiming he has information linking Gates to the gang. He sets up a meet, but when Arnott arrives he finds Gates colluding with the gang. Before he can escape, he is ambushed and tied to a chair, and his fingers are placed in a vice. Gates drives away, realising there is no way out. 5 5 `` The Probation '' Douglas Mackinnon 24 July 2012 ( 2012 - 07 - 24 ) 3.72 Gates returns to rescue Arnott from the hands of his torturers. Arnott, who is convinced that Gates is innocent of the murders and believes Gates can lead him to the killers, lies to Fleming and tells her that Gates did not play any part in his kidnapping. Meanwhile, with her cover blown, Fleming is forced to leave TO - 20, but not before Morton expresses his disgust. Cottan is assigned as deputy SIO on the triple murder case, while Arnott 's former counter-terrorism Chief Inspector is brought in to oversee the operation into apprehending the suspects. Fleming interviews Ryan, who denies any knowledge of ' Tommy ' or the murder of Jackie Laverty. He does, however, reveal to Fleming that it was Gates who rescued Arnott. Fleming, upset that her colleague has lied to her, informs Hastings. Meanwhile, Arnott uses Morton to set up a midnight rendezvous with Gates. Gates tries to convince Arnott that he has never ' crossed the line ', even once, and that he was forced to turn rogue and did not have any choice in the matter. Arnott persuades Hastings to let him use Gates to get to Tommy. Hastings agrees to put a tap on the phone network used by Tommy until one of his many phone numbers is re-activated. Arnott primes Gates, who convinces his wife to let him spend one final hour with his children. When the phone number is re-activated, Gates, Arnott and Fleming trail Tommy to the Edge Park golf club. Gates arrests Tommy. Under interrogation, Tommy reveals that his boys were responsible for the murder of Jackie Laverty and also took out the three drug dealers. Tommy claims that the murders were committed by ' an inside man, someone special to him ' who ' always follows orders ' and who would admit to them if he forced him to. As Arnott and Fleming catch up with them, Gates realises that his career is over and decides to commit suicide, telling Arnott to inform his wife that he was killed in the line of duty. After Tommy is arrested, Cottan has a quiet word with him. Tommy says, ' You tell me how I 'm going to play this one ', to which Cottan replies, ' Offer them all the information you can and plead immunity ', seemingly confirming that Cottan is Tommy 's inside man, later revealed as ' The Caddy ', having been recruited as a teenager when he caddied for Tommy at a local golf club. In an epilogue, Gates 's family receives a death - in - service benefit of £ 107,000 plus a pension for life. Arnott and his former counter-terrorism colleagues are acquitted of all charges. The evidence obtained on Tommy is never used, and he is put in the witness protection system. The case against Gates is closed. Series 2 ( 2014 ) The second series of Line of Duty -- consisting of six episodes -- premiered on 12 February 2014. The series follows DC Kate Fleming ( Vicky McClure ), DS Steve Arnott ( Martin Compston ) and Superintendent Ted Hastings ( Adrian Dunbar ) as they lead an investigation into the corrupt actions of DI Lindsay Denton ( Keeley Hawes ). The series ' supporting characters include DC Nigel Morton ( Neil Morrissey ) and DI Matthew Cottan ( Craig Parkinson ). Series two received even better reviews than its predecessor, despite lower viewing figures, and was ranked the best television drama of 2014 by The Observer. No. Overall No. in Series Title Directed by Original air date UK viewers ( million ) 6 `` The Ambush '' Douglas Mackinnon 12 February 2014 ( 2014 - 02 - 12 ) 2.74 A police convoy escorting a civilian under a witness protection scheme is attacked. The witness is hospitalised and all police officers are killed -- with the exception of Inspector Lindsay Denton, who organised the operation at very short notice and who only informed DCC Dryden. Ted Hastings asks Steve and Kate to investigate Denton, but Kate initially asks not to take part. She explains that she trained together with Jayne Akers, one of the dead officers, but she has also been having an affair with Jayne 's husband, Rich. She is replaced by Georgia Trotman, an ambitious but less - experienced officer who is troubled that the team are treating Denton as a suspect and delving into her finances. However, she and Steve quickly grow close, while Hastings tries to keep up appearances with his estranged wife. Denton, shunned by her fellow officers, is transferred to a missing persons unit, and Kate, undercover once again, becomes her assistant. Kate follows Denton to the nursing home where her mother lives and sees Denton ring the hospital where the injured witness is being treated. Georgia and Steve race to the hospital and confront a man disguised as a nurse. Steve is knocked unconscious ; Georgia, who sees the killer 's face, is thrown out of a window to her death, and the witness is killed. 7 `` Carly '' Douglas Mackinnon 19 February 2014 ( 2014 - 02 - 19 ) 3.21 Steve discovers that a nurse on the witness 's ward, Claire Tindall, was threatened into giving the killer access by a man she knows as Joe, but whom she is unable to identify. Denton begins her work in missing persons with the case of a vanished teenager named Carly Kirk. As they work together, Kate attempts to gain Denton 's confidence, but Denton sees through this, assaults Kate and steals her phone. Denton is interviewed again by AC - 12 and claims that she rang the hospital to ask that the witness exonerate her, but the team do not believe her and Hastings arrests her for conspiracy. At this point Denton turns the tables and gives evidence, on the record, that Steve made an unofficial romantic visit to Claire, Hastings has financial problems ( something he previously cited as making Denton vulnerable to bribery ) and Kate 's cell phone has an `` interesting '' call history ( alluding to her affair with Richard Akers ). Meanwhile, a story surfaces in the press that DCC Dryden took penalty points for his wife when she committed a driving offence. In a parallel sub-plot, Denton has a dispute with her alcoholic neighbour. The neighbour plays loud music late at night, and accepts cash in return for not doing so. One evening Denton snaps and strikes her with a wine bottle, which she then wipes down and disposes of. When the neighbour reports the attack, Denton flatly denies it. Again the music disturbs Denton, who finds her neighbour 's door open and the woman asleep, while a chip pan is heating up. On reflection, Denton turns the gas off, takes the money and leaves. 8 `` Behind Bars '' Douglas Mackinnon 26 February 2014 ( 2014 - 02 - 26 ) 3.34 Denton is remanded in custody, where she is victimised by both staff and prisoners, having her hands badly burnt and warned not to speak to the authorities. Hastings requests witness protection records from Dryden, allowing AC - 12 to discover the identity of the dead witness : Tommy Hunter, the gang leader previously arrested by Tony Gates. Cottan believes that the mole who betrayed the escort was in fact Jayne Akers, the liaison officer. Kate visits Denton, who knows about Kate 's affair with Jayne 's husband, which Cottan also suspects. Denton 's accusations also cause friction between Hastings and Steve, and Dryden 's driving offence continues to occupy the press. To draw attention away from himself, Dryden leaks the information that Denton is the officer under investigation. At the site where Denton stole Kate 's phone and blew her cover, Kate discovers a body, apparently that of the missing Carly. She re-interviews Denton, who claims that Dryden, a married man, had an affair with her and has set her up. Kate discovers that Dryden and Denton did previously work together, lending some credence to this story. Cottan discovers from forensic accountants that Jayne Akers received a large sum of cash shortly before she died. 9 `` Blood Money '' Daniel Nettheim 5 March 2014 ( 2014 - 03 - 05 ) 3.46 Steve and Kate persuade Hastings to bring Dryden in for questioning but find the DCC uncooperative and frosty. They face a further problem when the Major Violent Crimes team bring in Richard Akers before they can do so, as Steve mistakenly assumed that Richard was unaware of his wife 's corruption and so decided he was not a priority. When they do get to interview Akers, he reveals that Jayne kept recordings of Tommy as leverage and stored them at a PO Box. The recordings show Tommy threatening to inform on various parties, including corrupt police officers `` from the two - faced bastard right down to The Caddy '', unless they ensure his witness protection and immunity are maintained. A recording of Dryden publicly criticising the immunity Tommy and others like him receive suggest he is the corrupt officer in question, and AC - 12 begin seeking the identity of ' The Caddy '. Denton is granted permission to visit her dying mother at her nursing home, but on the return journey Denton 's prison van is run off the road. Fleeing for her life, Denton finds herself confronted by two corrupt police officers, including the man who murdered Georgia Trotman. 10 5 `` Last Words '' Daniel Nettheim 12 March 2014 ( 2014 - 03 - 12 ) 3.73 Denton manages to escape her kidnappers in violent circumstances that lead to the death of one and the hospitalisation of the other, and AC - 12 find themselves forced to decide where their loyalties lie between Denton and Dryden. With the evidence mounting against the latter, the discovery of pictures showing Dryden and 15 - year - old Carly Kirk in a compromising situation is the final nail in the coffin, resulting in Steve and Kate finally arresting the DCC. However, when presented with AC - 12 's evidence, Dryden still strongly maintains he is being set up. Meanwhile, Cottan approaches DC Morton from his old team. Morton is the officer who sold the story about Dryden 's driving offence to the papers, and Cottan blackmails him into falsely saying Jeremy Cole, the deceased kidnapper, was nicknamed ' The Caddy ' by fellow officers. 11 6 `` The Caddy '' Daniel Nettheim 19 March 2014 ( 2014 - 03 - 19 ) 4.12 Dryden claims that Denton was at the car park when he was photographed in the car with Carly. Steve gets closer to Denton but reveals to Kate that he is undercover, as she was earlier. Steve finds the pay - off money hidden among the possessions Denton took from her mother 's room. In flashback, the events prior to the ambush : Denton follows Dryden to the reception, where Carly meets and attempts to seduce him. Denton has a brief conversation with her in the ladies ' cloakroom and then follows Carly and Dryden to the car park, where she sees Carly fellate Dryden and that she is working for Tommy. Some days later, Denton approaches Tommy but is surprised to find him accompanied by DS Jayne Akers. Akers visits Denton at her home to request help in handing Tommy over to his criminal associates, who want to kill him out of fear he will inform on them in witness protection. With a pay - off, and appealing to Denton 's desire to protect Carly from her pimp and abuser, Akers persuades her to assist in the handover. In reality the handover is being planned by Cottan, the mastermind who is known only to Akers and Tommy. He orders two corrupt officers to ambush the convoy, who follow it using a tracker placed on Denton 's vehicle. Akers and Tommy are both killed to protect Cottan 's identity, Denton is left alive to take the blame. Details revealed in the epilogue : The buried body is not Carly 's, who has fled the country unknown to the authorities and criminal parties. DS Prasad, who carried out the ambush and kidnapped Denton gives evidence against her in return for complete immunity from prosecution. DC Morton is not suspected of any wrongdoing and will retire in a year on full pension ; he continues to sell confidential information to the press. DCC Dryden is given a suspended sentence for perverting the course of justice regarding his wife 's speeding ticket and resigns from the police force. Denton is convicted of conspiracy to commit murder and given a life sentence. Cottan is asked to remain in AC - 12. Major Violent Crimes continue to investigate who organised Tommy 's murder, but no police officers beyond Denton are suspected. Series 3 ( 2016 ) The third series of Line of Duty -- consisting of six episodes -- premiered on 24 March 2016. The series follows DC Kate Fleming ( Vicky McClure ), DS Steve Arnott ( Martin Compston ) and Superintendent Ted Hastings ( Adrian Dunbar ) as they lead an investigation into the corrupt actions of Sergeant Danny Waldron ( Daniel Mays ). The series ' supporting characters include DC Nigel Morton ( Neil Morrissey ), DI Matthew Cottan ( Craig Parkinson ), and DI Lindsay Denton ( Keeley Hawes ). The storyline in this series is a direct continuation of the second series ' plot. No. Overall No. in Series Title Directed by Original air date UK viewer ( millions ) 12 `` Monsters '' Michael Keillor 24 March 2016 ( 2016 - 03 - 24 ) 3.54 Sgt. Danny Waldron and his team of armed officers are deployed to detain Ronan Murphy, a suspect wanted in connection with a plot to commit a gangland execution. Waldron orders a ' hard stop ' on the suspect 's vehicle, forcing the suspect to decamp into a nearby housing estate. Waldron gives chase, but catches up with him long before his team arrive. Waldron decides to shoot the suspect in cold blood, despite him having already surrendered his gun, and fakes the scene to make it look like he opened fire before he was shot. When Waldron 's team arrive, he orders them to discharge their weapons. Under interrogation from AC - 12, Waldron looks to have an answer for everything, until DS Arnott 's line of questioning into his private life begins to spook him. Hastings agrees to send Fleming undercover as a new member of Waldron 's squad in an attempt to uncover the truth. Waldron 's team are tense as a result of being bullied into collaborating with Waldron, and Fleming identifies PC Harinderpal ' Hari ' Bains as a possible informer, but Bains refuses to testify. After pressure from AC - 12 department lawyer Gill Biggeloe, Waldron 's team are returned to active duty along with Fleming. On their first call, they are tasked with raiding a house where drugs are kept. Waldron steals an illegal firearm, then stops Fleming from aiming her gun at a child who surprises them. Waldron demands Fleming transfer out of his squad. Waldron lingers outside Bains ' house with the stolen gun, but leaves when spotted. He later spies on Ronan Murphy 's funeral. He follows Linus Murphy, one of the mourners, breaks into his house, and holds him at gunpoint, implying as he does so that Ronan and Linus were part of a group who abused him as a child, and that he killed Ronan for revenge. He murders Linus off screen and returns to his flat, where he leaves a list of names including Ronan, Linus and Tommy Hunter in an envelope addressed to Arnott. Waldron 's team raids another drug house, where he orders Fleming to stay behind while the rest of the team search upstairs. Fleming hears shots fired, and rushes upstairs to find the other squad members standing around Waldron, who has been shot in the neck. 13 `` The Process '' Michael Keillor 31 March 2016 ( 2016 - 03 - 31 ) 6.02 Kate Fleming attempts to provide first aid to the wounded Sgt. Waldron, who dies in the ambulance. The remaining members of the team, PC Rod Kennedy, PC Hari Bains and PC Jackie Brickford, are interviewed by AC - 12 and claim Waldron shot himself despite their attempts to stop him. Hastings attempts to arrest them, but Gill Biggeloe convinces him to rescind the arrest. The police search Waldron 's flat, finding Linus Murphy 's dog ( who Waldron took with him after the murder to help lead the police to Murphy 's body ) and DI Cottan discovers a box containing the stolen gun, a photograph of a young Waldron and other boys alongside Ronan and Linus Murphy, and the envelope, addressed to Arnott, containing Waldron 's list. Cottan steals the list. Arnott agrees to take over the investigation of Waldron while Cottan focuses on his colleagues. Arnott locates Linus 's home and finds his tortured and decapitated body, then finds the head in a storage room rented by Waldron. Waldron 's team - mates find themselves suspected by their colleagues, and Fleming pressures them further by suggesting she knows they murdered Waldron, and indicating she will tell AC - 12 about a radio call Bains made to Waldron moments before his death, which was not included in the reports. Meanwhile, Lindsay Denton has appealed against her conviction for conspiracy to murder Tommy Hunter, and Arnott is called as a witness. He denies having a sexual relationship with Denton, but the suggestion puts strains on his relationship with his girlfriend, DS Sam Railstone. Scared by pressure from Fleming, Kennedy demands to meet Bains in a disused warehouse, blaming Bains for their situation. This results in a brief physical confrontation. Denton claims in court that she had sex with Arnott. Next morning, Kennedy 's body is found hanged in the warehouse where he confronted Bains. Brickford and Bains meet, and appear the next morning to alter their statements to AC - 12. They now claim Kennedy shot Waldron, and Brickford confesses she had a relationship with Kennedy until some months earlier, when they broke up after she had a one - night stand with Waldron. Bains receives a package containing a phone, and receives a call from someone who congratulates him on his deception. 14 `` Snake Pit '' Michael Keillor 7 April 2016 ( 2016 - 04 - 07 ) 5.73 Hastings authorizes Fleming to begin surveillance of Hari Bains. She watches him meeting with Jackie Brickford ; when Arnott interviews Bains ' superior, Bains panics and is observed calling his contact from a payphone. Fleming asks Cottan to organize a second examination of Rod Kennedy 's body, which Cottan intentionally neglects to do. The photo of Waldron and Ronan Murphy is traced to his time in Sands View boys ' home. Arnott identifies Joseph Nash, another boy in the picture, and interviews him. Nash explains Linus Murphy was the caretaker at Sands View, that both men abused boys at the home, and that boys at the home were sexually abused by other men both at Sands View and at private parties. He identifies then - Councillor Dale Roach, but Roach is unable to stand trial, due to a stroke. Brickford visits Fleming to find out what AC - 12 has been asking her. Fleming reveals Bains has been making phone calls, seemingly to Brickford. Brickford confronts Bains, who can not explain the calls. Brickford returns to AC - 12 and confesses Waldron was shot in a struggle that Brickford and Kennedy were involved with. Only Bains saw how it began. Bains claimed Waldron had aimed at him, and that Bains grabbed the gun in self - defence. Brickford also confesses to lying about Ronan Murphy 's death. Hastings has Brickford 's police contract terminated and warns her she may yet be charged. Meanwhile, Arnott orders a second post mortem on Rod Kennedy 's body. It indicates he was murdered. AC - 12 moves to arrest Bains and the firearms unit are deployed to arrest him, but his contact ( revealed to be Cottan ) warns him and he escapes. He travels to the warehouse where Kennedy was hanged, and finds Cottan ( unaware that Cottan is his contact ). As the firearms team approach, Cottan handcuffs and injures himself to fake a fight. Bains is arrested and the police find a noose, supporting Cottan 's story that Bains was attempting to hang him. Lindsay Denton 's trial reaches its conclusion. The jury finds her not guilty of conspiracy to murder, and she is released with time served. She tells Arnott she forgives him, outside the courthouse. Cottan is congratulated by his colleagues, but the unregistered phones in Bains ' home suggest he was acting on orders, and, as Cottan watches TV news footage of Denton 's release, a number of mobile phones in his house begin to ring simultaneously. 15 `` Negative Pressure '' John Strickland 14 April 2016 ( 2016 - 04 - 14 ) 5.55 Lindsay Denton is taken to AC - 12, where she demands a formal apology. She reveals she has a recording of herself and DS Steve Arnott in a compromising situation that she will use against him as evidence of perjury if they do not comply with her requests. Denton is forced to work as a supermarket cleaner and later entraps an exploitative parole sponsor trying to pressure her into sex. Arnott -- who is losing confidence within the department -- eventually meets with Denton and asks for help in finding the link between Sands View and Tommy Hunter. DI Matthew Cottan is awarded with a commendation for his perceived bravery arresting a corrupt police officer, Hari Bains. He then proceeds to tell Gill and DC Kate Fleming he is concerned about Steve 's behaviour and that Steve is carrying a firearm in his jacket. Bains confesses to killing Danny Waldron on the demands of his unknown contact, but insists he did not murder Rod Kennedy. Steve and Kate confront Ted, saying they believe they should question a retired officer on the subject of allegedly reporting to a mother that a sexual - abuse complaint of Dale Roach was dealt with, resulting in Roach being charged and sent to prison. The mother saw Dale Roach in the newspaper some time later, so knew she had been lied to. The death of a former social worker at Sands View, ruled as a suicide, is reinvestigated due to allegations that he attempted to report the abuse to police and may have been murdered to prevent his case being pursued. They eventually interview former vice chief superintendent Fairbank, who claims to remember no details of the case. He and Hastings share a handshake that Arnott identifies as Masonic. Cottan meets former colleague Nigel Morton and threatens to derail his pension if he does not hand over the last known evidence of Cottan 's true allegiance -- a mobile phone and SIM card with records of calls made to Hunter. Morton tells AC - 12 the Caddy is probably still alive, leading Cottan to create a presumptive profile which he deliberately engineers to fit Arnott. Morton hands the phone and SIM to Cottan in a car park ( where Cottan was prepared to kill him if he had not complied ), but it is then revealed it was a duplicate and Morton still has the real items hidden in his car. 16 5 `` The List '' John Strickland 21 April 2016 ( 2016 - 04 - 21 ) 5.72 Cottan continues to stack the deck against Arnott, first by pressurising PC Maneet Bhandra to hold off on key forensics ( specifically the envelope found in Danny Waldron 's flat ), and then by spreading rumours surrounding Arnott 's conduct, including telling Fleming he has a lead linking Arnott to Lindsay Denton 's bribe money. Arnott is eventually suspended by a hesitant Hastings, to whom he reveals the redacted file that would have linked Ronan and Linus Murphy to Tommy Hunter. Hastings challenges Gill on this but is rebuffed. Meanwhile Fairbank is called in for interview and maintains his ignorance as he is presented with images of alleged abusers, such as councillor Dale Roach and real - life BBC DJ Jimmy Savile ( who is not identified by name in the show ). Joseph Nash is shown a photograph of Fairbank, ostensibly to identify him as an officer that had overlooked accusations, but his reaction suggests Fairbank was one of the abusers. Arnott continues to meet with Lindsay Denton as they investigate the possibility of Danny Waldron hiding another copy of his list of abusers. Denton realises the list is likely kept digitally, so she tricks Arnott into pursuing a false lead while she, after stealing Arnott 's pocketbook, goes to an internet cafe to access Waldron 's emails. She finds a photograph of the list in his drafts folder and transfers it to hers as insurance. Outside, Cottan -- who has been following Denton -- summons her into his car, revealed to be DS Arnott 's service vehicle with fake licence plates, and drives her to an industrial facility demanding at gunpoint she hand over the information, offering money for her obedience. Denton, staying true to her morals as a former police officer, defiantly emails the list to Hastings. Cottan murders Denton but is too late to prevent the list being sent. 17 6 `` Breach '' John Strickland 28 April 2016 ( 2016 - 04 - 28 ) 5.93 Patrick Fairbank is arrested and interviewed on new information submitted by Joe Nash during an identity parade. During the interview, Hastings receives the list sent by Lindsay Denton which identifies Fairbank as one of the abusers. Meanwhile, Arnott awakens to find his pocketbook missing and his car stolen. As he reports the car missing, Hastings attends a call to a dockers ' yard where the body of Lindsay Denton has been discovered in Arnott 's car. Arnott is arrested on suspicion of murder. During questioning, evidence identifying Arnott as ' The Caddy ', such as money from Lindsay 's Denton 's bribe and the mobile phone he used to contact Hari Bains, are shown to have been found in Arnott 's gym bag. Arnott realises the evidence records relating to his hiring of a firearm have been doctored to suggest he did not return it. He knows somebody within the department has set him up, but has no way of proving it. Cottan then reveals, much to the surprise of Hastings and Fleming, he has suppressed the evidence found in the envelope left to Arnott by Danny Waldron, and that the evidence is a golf tee, supposedly confirming that Arnott is ' The Caddy '. Fleming informs Hastings she has been carrying out an undercover operation into the officers of AC - 12, under the orders of a superintendent from AC - 3. She highlights inconsistencies within Cottan 's line of questioning against Arnott. Having spoken with DS Nicola Rogerson, she identifies Cottan was the one who fed AC - 12 the doctored file on Ronan Murphy. Hastings confronts Gill Biggeloe, who confirms it was Cottan who gave her the file. Maneet later reveals to Fleming it was Cottan who told her not to inform Arnott of the forensic findings of the envelope found in Waldron 's flat. Fleming also uncovers CCTV which confirms Arnott 's car was being driven on false plates shortly before the time of the murder. Cottan is brought in for questioning. He denies all knowledge of the doctored file and claims Arnott must have been the one responsible, having previously had a relationship with DS Rogerson. Hastings pressures Cottan on the suppression of the golf tee from evidence, as well as the fact that no blood was found on the tee despite blood being found on both the envelope and the list. Cottan claims he only removed it to prevent Arnott from becoming aware he was investigating him. Fleming reveals new forensic evidence against Cottan -- fibres from the rope found at Rod Kennedy 's murder scene, in the boot of his car. Cottan strenuously denies any involvement with Kennedy 's murder. Hastings probes him on evidence submitted by Nigel Morton, which suggests he pressured Morton into wrongly identifying ' The Caddy ', and also used a secret mobile phone. Phone records reveal he previously called Tommy Hunter several times in the months leading up to his death. Fleming presses Cottan on the lead he claimed to have on Arnott linking him to Lindsay Denton 's bribe, which Hastings points out could not have been the money in Arnott 's gym bag as that was not discovered until after Denton had been killed, the morning after Cottan alleged to have evidence against Arnott. Questioned about his whereabouts on the morning of Lindsay Denton 's murder, Cottan fails to provide a solid alibi, and Fleming reveals that he was not at his flat when he claimed he was. Cottan sends a text to three recipients, ' Removals ', ' Talk ', and ' Ride '. An armed officer guarding the interview shoots a fellow armed officer dead, fires shots into the interview room, enabling Cottan 's escape, and then hands Cottan a pistol. Pursued by an armed Fleming, Cottan is rescued by a getaway car. Fleming manages to shoot the driver and brings the car to a standstill. As she goes to confront Cottan, another passenger fires three shots aimed at her, but Cottan jumps in front of her, taking the bullets. In a final act of redemption, Cottan records a dying declaration that directly leads to Fairbank being jailed for ten years. The epilogue reveals Arnott is exonerated, Fleming is awarded for her bravery and later promoted to Sergeant, Denton receives posthumous recognition for her contributions by the coroner but is buried with no mourners, and Nigel Morton retires on full pension plus disability benefits. The epilogue also states Hastings, Arnott, and Fleming remain with AC - 12. Series 4 ( 2017 ) The fourth series of Line of Duty, consisting of six episodes, began broadcasting on 26 March 2017 on BBC One. The story follows DS Kate Fleming ( Vicky McClure ), DS Steve Arnott ( Martin Compston ) and Superintendent Ted Hastings ( Adrian Dunbar ) as they investigate the actions of DCI Roseanne Huntley ( Thandie Newton ). The supporting characters include FC Tim Ifield ( Jason Watkins ), DC Jodie Taylor ( Claudia Jessie ), and DS Sam Railston ( Aiysha Hart ). As with the previous two series, the storyline is linked thematically to that of series 1. No. Overall No. in Series Title Directed by Original air date UK viewer ( millions ) 18 `` Episode 1 '' Jed Mercurio 26 March 2017 ( 2017 - 03 - 26 ) 9.21 DCI Roz Huntley identifies and captures a suspected serial killer. The suspect is uncooperative under questioning and appears not to have an alibi. After months of fruitless investigation, ACC Derek Hilton puts pressure on Huntley to charge the suspect. Forensic Coordinator Tim Ifield informs Huntley of concerns he has relating to the forensic evidence, which he believes proves the suspect 's innocence, but Huntley seems uninterested. Ifield alerts AC - 12 to a possible miscarriage of justice. Tim tells Steve Arnott he believes DCI Huntley is deliberately ignoring forensic evidence which proves the suspect 's innocence. Tim explains the forensics suggest someone has manipulated the crime scene in an attempt to frame the suspect. With the authorisation of Ted Hastings, Kate Fleming goes undercover to investigate Huntley, and also interviews the suspect. Arnott informs Huntley that AC - 12 are investigating. Huntley suspects Ifield and turns up at his house at night, where she accuses Ifield of talking to AC - 12. Ifield admits this, and a row breaks out over the guilt of the suspect. Huntley scalds Ifield 's hand on a hot pan, and Ifield slaps Huntley. Huntley then accuses Ifield of assault. Ifield pushes Huntley, who hits her head on a table and becomes unconscious. Realising Huntley has no pulse, Ifield sets about disposing of the body. 19 `` Episode 2 '' Jed Mercurio 2 April 2017 ( 2017 - 04 - 02 ) 9.04 When being interviewed by DS Fleming, Michael Farmer correctly gives the name of the hospital he was in when Leonie Collersdale, the second murder victim, was killed, throwing further doubt on his guilt. Worries grow when DCI Roz Huntley fails to report for duty. A dismembered female body is discovered, Leonie Collersdale 's. When she reappears, Roz brushes off her absence, saying she had some kind of bug. ACC Hilton tells Roz that Hastings is going to serve her with a Regulation 15 notice. AC - 12 interviews Roz and throws doubt on forensic evidence concerning the attack on Hana Reznikova, which Roz alleges is by Michael Farmer, and says Roz failed to present any contrary evidence to the Crown Prosecutor. Hastings says he will be recommending she be taken off the case. Roz is shown examining Ifield 's laptop in her car. Tim Ifield is missing ; DS Arnott goes to his flat, breaks in and finds his body. Three fingers had been amputated. Roz arrives and takes charge of the crime scene, despite Steve 's protests. Inside, she notices the blood spatter on the edge of the kitchen counter, which is hers. She hears the sample being labelled KRG - 13, but notes it incorrectly as KRG - 30. Roz obtains a sample of Ifield 's blood from her car, labelling it KRG - 30. Managing to gain access to the forensic samples, she can not find KRG - 30, but realises her error and over-writes her sample bag as KRG - 13. Ifield 's mobile phone records are investigated, and communications with Hana Reznikova are found. DS Arnott finds from forensics that Ifield was probably wearing a white forensic oversuit at the time of death. Summarising the evidence, he implies to Hastings that Roz is Ifield 's killer. Roz takes a further sample of Ifield 's blood and inserts it into forensic submissions for Leonie Collersdale 's murder, implicating him. She requests further forensic tests ; forensics find the match to Ifield. DS Fleming passes the Inspector 's exam. Hastings has chats with both her and DS Arnott, and indicates informally to Kate he has decided on Arnott for promotion. Roz tells ACC Hilton that, if AC - 12 's informant was Ifield, the evidence against him undermines his evidence and therefore undermines the case against her. She tells him she 's convinced Tim Ifield 's murder and Michael Farmer 's crimes are connected. 20 `` Episode 3 '' John Strickland 9 April 2017 ( 2017 - 04 - 09 ) 9.05 Roz continually shuts Kate out of the investigation meetings. The officers try to find links between Tim Ifield and Michael Farmer. In order to gain access to information from the investigation, AC - 12 seize evidence forcibly, since Kate is unable to gain access undercover. A security camera shot of Ifield in the balaclava mask and purchasing the cutting tools found at his flat does not convince Steve that Ifield is Balaclava Man. His requests to Hastings to open a second investigation are authorised. Steve theorises Roz was the one to kill Ifield after her phone history proves suspicious. A note to Roz left on her computer warns her she is being watched and she soon suspects Kate. Jody notices Kate checking the forensics ( that Roz had swapped ) and reports back to Huntley. Roz interviews Hana, the victim of Balaclava Man, whom she saved originally, and, having discovered Hana is a prostitute who had had sexual encounters with Ifield, sets about framing her for his murder. Steve begins questioning Nick Huntley about his wife 's whereabouts on the night Tim died, but Nick refuses to confirm or deny his wife 's alibi. A new DC, Jamie Desford, is assigned to Steve to assist him. Having heard no response from Nick, Steve returns to his office to question him and misses various voice messages from AC - 12 warning him Nick could be dangerous as his car was identified both approaching and departing from the area near Ifield 's flat on the night of the murder. On the way up in the lift, Steve is attacked by a man in a balaclava, hit in the face with a baseball bat and thrown down the stairs. With blood pooling round his head, his fate is left uncertain. 21 `` Episode 4 '' John Strickland 16 April 2017 ( 2017 - 04 - 16 ) 9.60 After the attack on DS Arnott, Roz picks up husband Nick outside his offices and advises him to go back inside away from CCTV and ask security to look for Steve Arnott. Arnott is found to be badly injured, but alive. Nick is interviewed by Superintendent Hastings and DC Jamie Desford. Nick says it was a complete coincidence that only he knew Arnott was to be at his office building when he fell down three flights of stairs. He did not explain why his car was seen near Ifield 's flat when Ifield was murdered. Nick said his wife Roz was asleep in the spare room that night. Nick 's solicitor, Jimmy Lakewell, says very officiously that with no evidence or CCTV Nick should be free to go. AC - 12 find a CCTV image of a man in a balaclava by Nick Huntley 's offices at the time of the attack on Steve. In her car, Nick and Roz argue, Nick saying he had seen Roz going into Ifield 's flat 's building that night. Roz says she was having an affair. Quizzed by Hastings in hospital, Steve is unable to identify his attacker. At a meeting in his club, Roz appeals for ACC Hilton to help her by making an official complaint against AC - 12 and closing the case against Michael Farmer. Hilton says there are some things he could tell Roz to help her with AC - 12. Despite her friendliness, she rejects his advances, but suggests they meet again. Roz and then DS Fleming talk with Kevin Gill, the forensics officer KRG. Roz 's wrist injury is now considerably worse ; she has it examined by a doctor, who takes a swab. Roz and Nick argue again, at home. Nick says he ca n't believe anything she says any more and he knows she was in the flats where the murder happened. She slaps him, twice ; he breaks down. AC - 12 finds an anomaly in the second forensic examination of KRG - 13, the blood - spatters sample with the overwritten label : traces of white fibres from a forensic oversuit. Roz is interviewed by AC - 12. Hastings appears to have the upper hand. After running through evidence, he says he will be recommending she be suspended from duty immediately. Roz then turns the tables, accusing Hastings of sexism. She has identified DS Fleming as an undercover AC - 12 officer in her team. Roz asks Hastings whether he is a mason. All through this altercation, a clearly - rattled Hastings is asking her where she is getting this information. She suggests DS Flynn was induced to tamper with evidence concerning Ifield 's murder, accuses Hastings of a conspiracy to pervert the course of justice in the case against her, and brandishes a supporting letter from ACC Hilton, recusing AC - 12 from their inquiry. Hilton and Roz meet again at his club, but Roz again rejects him, saying she loves her husband. Afterwards, PC Maneet Bindra is seen handing a file to ACC Hilton. 22 5 `` Episode 5 '' John Strickland 23 April 2017 ( 2017 - 04 - 23 ) 9.98 Hastings accuses ACC Hilton of a wilful effort to bury allegations of wrongdoing. Hilton denies this and demands a copy of the recording of Matthew Cottan 's dying declaration ( `` DD '' ). Hastings declines, claiming no reciprocity. At a team briefing, DS Neil Twyler reports biometrics suggest Balaclava Man who attacked Steve Arnott and Balaclava Man seen in the area of Leonie Collersdale 's murder are the same man. Roz says maybe, but Michael Farmer may change his plea to guilty. Neil clearly has doubts and tells a colleague Roz is so keen to pin Ifield 's murder on Hana. Kate tells Hastings the leak of her cover is likely to have been from within AC - 12. More female body parts are discovered : they are more of Leonie Collersdale. Steve arrives back in the office, returning to work despite his immobility. He 's in a wheelchair. He says Roz can not be allowed to mislead the investigation and Hilton said nothing about AC - 12 not investigating Ifield 's murder. He suggests looking at Nick Huntley 's alibi, and Maneet finds it does not clear him. Maneet asks Jamie for his username and password, claiming they 're being changed, then uses them to enter the system and download a copy of the recording of Cottan 's DD, which she passes to Hilton. Soon after, Maneet asks to finish work, due to the strains of her pregnancy. Later, Kate notes the sensitive information access and tells Hastings, who gives Jamie a dressing down. Jamie says he is being scapegoated, requests a transfer and leaves the office. Steve visits Michael Farmer in prison, suggesting a change of solicitor ; Farmer says he liked the one he had before. Steve has Farmer 's Nan visit to try to prevent him from changing his plea ; she succeeds. Steve tells Kate the framing of Farmer could not have been random and finds Farmer 's earlier solicitor was Jimmy Lakewell. Steve and Kate visit Lakewell, but get nowhere. Roz 's wrist injury is worsening ; Nick says it 's stinky ; the doctor who took the swab tries to contact her. At home, she faints after taking off the dressing. Nick meets Lakewell, saying Roz is lying and has a wound which dates from the night of Ifield 's murder. He thinks Roz murdered Ifield. Lakewell floats the idea of a voluntary interview and immunity. Forensics ( Rupal ) reveals proof the latest remains had been frozen and were buried after both Farmer 's incarceration and Ifield 's murder, and suggests a team briefing to Roz. Rupal goes to the team office for the briefing she expects to take place, but no - one has been made aware of the information. Neil, who hears this, meets Kate and, stressing anonymity, relays the information. This triggers Steve 's memory : Jackie Laverty 's body ( series 1 ) was buried after being kept in deep freeze. Men in balaclavas with baseball bats were involved. He suggests the Laverty case, which is unsolved, be re-opened, giving them the chance to examine the latest forensics. Roz is in hospital. Nick explains to her that her hand had to be amputated to save her life. With the new forensic evidence, Steve finds the blood sample of Ifield ( relating to Leonie Collersdale 's murder ) was contaminated with white forensic oversuit fibres, just as the blood spatter on the kitchen counter had been. So both were falsified. He says he believes Roz has been protecting Nick. Hastings says `` to hell with ACC Hilton '' and tells Kate to go and pick up both Roz and Nick Huntley. But Roz had discharged herself from hospital. Roz 's sidekick Jodie picks Roz up and tells her Lakewell has requested a voluntary interview with independent detectives about Ifield 's murder, seeking immunity. Nick meets Roz at home. She says they 're getting a divorce and accuses him of amputating her hand in retribution for her having an affair. He says it was all her lies and she had MRSA in her wound. She arrests him for Ifield 's murder. Once Nick has been taken away, Roz reaches for the holdall she 'd retained which contains contaminatory items from the scene of Ifield 's murder and runs his hairbrush over one of Nick 's pullovers. Hastings, Steve and Kate visit ACC Hilton. Steve and Kate explain evidence was planted in order to falsely implicate Ifield in Leonie Collersdale 's murder and that Ifield had uncovered a conspiracy to frame Michael Farmer for the murders. Hastings says he 'd like to arrest Roz straight away on suspicion of perverting the course of justice. Hilton brushes all this aside and reminds them of the recusion of AC - 12, and that these are Roz 's cases. Hastings says they came across this as a result of looking again into the disappearance of Jackie Laverty. Hilton looks disturbed by this revelation, then praises their work, but again calls for their files to be handed over to a more impartial authority. Hilton tells Steve and Kate to leave and plays the recording of Cottan 's DD to Hastings. Hastings protests vehemently. From the DD, the ' top dog ' ( top corrupt policeman ) promoted Cottan and his name began with H. Hilton tells Hastings, calling him H, that he will be served with a Regulation 15 notice, with 10 working days to answer the allegations, and dismisses him. Kate drives Steve home, where he is not able to look after himself. He confesses to Kate he may never walk again ; Kate consoles him. Before he is interviewed, Nick again tells his solicitor Roz is lying about everything. 23 6 `` Episode 6 '' John Strickland 30 April 2017 ( 2017 - 04 - 30 ) 10.40 Nick Huntley is interviewed regarding his movements on the night of Ifield 's murder. AC - 12 realise it is consistent with the few CCTV recordings and witness testimonies they have, but struggle to find any evidence to implicate Roz. Jamie has transferred to ACC Hilton 's team and is thus in conflict with AC - 12, further complicated by the fact his partner is Arnott 's ex-girlfriend. Roz leads them to Nick 's tampered jumper, which allows Polk Avenue to formally charge him with Ifield 's murder, as well as the previous crimes attributed to Balaclava Man. Nick asks Lakewell to get AC - 12 involved, but he declines. Roz also asks Jodie to analyse some telecoms on the quiet. Arnott realises Ifield 's killer stole a tracksuit, as his or her clothes were covered in blood, and then would probably have changed clothes again when they got home before hiding both. They try to narrow their search to a specific time and area, managing to find a three - hour window shortly after Ifield 's murder, and are able to spot Roz driving towards a large area of woodland. They also discover the MRSA that infected Roz 's wound is likely to be traceable in Ifield 's balaclava. Arnott works out the time taken for Roz to drive to and from the area would have only given her a few minutes to hide the evidence. They find out she led a previous search of the area and that she hid her own incriminating evidence in the same place. Roz is subsequently arrested for Ifield 's murder and requests Lakewell as her solicitor. After being interrogated and facing damning evidence against her, Roz admits to Ifield 's accidental death in self - defence and to framing Nick. Just as the interview appears to be concluding, Roz arrests Lakewell for perverting the course of justice. It is revealed that Lakewell, whom Nick rang immediately when Arnott was approaching his office, tipped off ACC Hilton using a ' burner ' phone, and Hilton tipped off the man who attacked Arnott. Roz is able to prove Hilton 's involvement as he gave her his number when attempting to seduce her. Hastings and Fleming head to Hilton 's office, but Jamie has tipped him off and he has already gone by the time they arrive. Jamie attempts to leave with Lakewell, but Arnott and Roz stop him, saying he has probably been set up to be murdered. Hastings and Fleming return but one of the balaclava men ( Lakewell admits there are many ) holds a security guard at gunpoint. Hastings promptly shoots him. When they get upstairs, Jamie has pulled a gun on Arnott. However, Hastings and Arnott are able to persuade him to drop his firearm. Hilton is found dead the next day, ruled as a suicide but at the same location as a murder relating to the Sands View child - molestation ring. As the dust settles on this particular case, Hastings, seemingly no closer to untangling the bigger conspiracy, admits he thinks this has become a life 's job. The epilogue reveals Roz was sentenced to ten years for Ifield 's manslaughter and the subsequent cover - up. She and Nick remain married. Lakewell pleaded guilty to perverting the course of justice, but declined witness protection and refused to testify. Michael Farmer was released without charge, and the Regulation 15 order against Hastings was dropped. Hastings remains in charge of AC - 12. Series 5 The fifth series is due to start filming in September 2018. Series 6 The BBC announced the commission of a sixth series on 5 May 2017. References Jump up ^ Series 1 - 2 based on 7 day data. Series 3 - 4 based on 28 day data. Jump up ^ `` Line of Duty - Cops unter Verdacht - Season 1 ''. Amazon.de. Retrieved 2 May 2017 -- via Amazon. ^ Jump up to : `` BARB ''. BARB. Retrieved 16 February 2014. Jump up ^ Hogan, Michael ( 26 February 2014 ). `` Line of Duty review ''. The Telegraph. Jump up ^ Munn, Patrick ( 27 February 2014 ). `` Ratings : BBC2 's Line of Duty Remains Steady ''. TV Wise. Jump up ^ Ferguson, Euan ( 7 December 2014 ). `` The best British TV Dramas of 2014 ''. The Observer. Jump up ^ `` Line of Duty - Cops unter Verdacht - Season 2 ''. Amazon.de. Retrieved 2 May 2017 -- via Amazon. Jump up ^ `` Line of Duty - Cops unter Verdacht - Season 3 ''. Amazon.de. Retrieved 2 May 2017 -- via Amazon. Jump up ^ 28 day data Jump up ^ `` Top 30 Programmes -- BARB ''. barb.co.uk. Retrieved 2016 - 02 - 11. Jump up ^ `` BBC Two celebrates 50th birthday with ambitious new commissions ''. BBC Television. British Broadcasting Corporation. 8 April 2014. Retrieved 31 May 2014. Jump up ^ `` BBC Two announces Jed Mercurio 's Line Of Duty commissioned for further two series ''. BBC Television. British Broadcasting Corporation. 8 April 2014. Retrieved 31 May 2014. Jump up ^ `` Line of Duty to move to BBC1 for two more series ''. Radiotimes.com. Retrieved 15 July 2016. Jump up ^ `` Line of Duty to begin filming series 5 ' in one month ' ''. Radiotimes.com. Retrieved 18 August 2018. Jump up ^ `` Line of Duty WILL be back for a sixth series ''. bbc.co.uk. Retrieved 6 May 2017. Retrieved from `` https://en.wikipedia.org/w/index.php?title=List_of_Line_of_Duty_episodes&oldid=856912499 '' Categories : Lists of British crime television series episodes Lists of British drama television series episodes Hidden categories : Wikipedia articles with plot summary needing attention from March 2017 All Wikipedia articles with plot summary needing attention Talk Contents About Wikipedia Deutsch Edit links This page was last edited on 28 August 2018, at 10 : 09 ( UTC ). Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: how many episodes in season 1 of line of duty
Answer: 5