The Ambassadors of Death ( TV story ) The Ambassadors of Death was the third story of season 7 . It was the final story to be written by former script editor David Whitaker , and was the Third Doctor ' s first adventure into space without the use of his TARDIS It also featured the first instance the TARDIS console was shown in colour format , and for that matter , removed from the TARDIS entirely . The Doctor had disconnected it and moved it to a study room inside UNIT headquarters now that his TARDIS was rendered inoperative , needing to utilise it in his experiments . Synopsis . The Doctor joins UNIT ' s investigation of the mystery surrounding " Mars Probe 7 " . Space Control , headed by Professor Ralph Cornish , has had no contact with the astronaut s on board since it started back from Mars seven months ago . Now the " Recovery 7 " rescue mission has run into similar difficulties . This second ship gets back to Earth , but the astronauts are kidnapped after landing , and Liz Shaw notices that the Geiger counter is at maximum . It transpires that the ship ' s occupants were not the human astronauts after all but a trio of radiation - dependent alien ambassador s who had swapped places with them . The Doctor makes a solo flight in " Recovery 7 " and docks with " Mars Probe 7 " , still orbiting in space . He is intercepted by a huge , alien spaceship and taken on board , where he finds the real astronauts unharmed . The aliens ' captain threatens to destroy the Earth unless their three ambassadors are released . The Doctor is allowed to go and , after returning to Space Control , discovers that the kidnapping of the ambassadors is part of a scheme devised by xenophobic ex - astronaut General Carrington to discredit the aliens and convince the world ' s authorities to wage war against them . The Doctor and UNIT thwart his plans and arrange the safe exchange of ambassadors for astronauts . Plot . Episode 1 . An astronaut is bearing down on " Mars Probe 7 " . There has been no contact between the probe and Earth for seven months when it took off from Mars . The Brigadier , who is overlooking the proceedings in the Space Centre , asks Professor Cornish , who is running the recovery mission , if he considers them to be dead . Cornish says he suspects so . The whole recovery mission is being televised live . The Doctor is trying to reactivate the Time Vector Generator using his TARDIS control . He inadvertently sends Liz fifteen seconds into the future before doing so to himself — much to her confusion . The Doctor notices the Brigadier on television . He is still bitter about the Brigadier ' s decision to destroy the Silurians . The recovery vessel is about to link up with the probe . The Brigadier asks the astronaut if he is sure the probe is " Mars Probe 7 " . He says it is . He tries for radio communication one last time and then begins the process of linking up . The Doctor watches , enthralled . The astronaut activates the airlock . The air holds . He goes to open the hatch and hears something on the other side . He thinks he hears the hatch in the probe open . He opens his own hatch . Communication is lost in the Space Centre . All they hear is a shrill noise that hurts the ears of everyone listening . When it is done their is no contact . Back at UNIT headquarters , the Doctor recognises the sound but can ' t place from where . He and Liz set off for the Space Centre . Cornish is told there are no issues with any of the equipment at the Space Centre , so it must be an issue on the vessels . One of the other doctors , by the name of Taltalian , is being interviewed but gets frustrated with the journalist and walks off . The Doctor drives into the Space Centre directly after another vehicle , much to the concern of the guards . The probe is holding its position . One of the scientists wonders if it was an excess of electricity built up in the probe that may have fried the communications but not killed the astronauts . The Doctor arrives , pursued by soldiers that are called off by the Brigadier . The Doctor says that the sound is a message . Cornish is dismissive of the Doctor , but the sound returns . The Doctor identifies it as a series of high frequency accelerated impulses . He demands unlimited computer time and multiple copies of the recording so as to analyse it . Cornish ' s back is still up . The Doctor becomes more consolatory to him , and he calms down . The sound appears again — but this time it is slightly different . The Doctor states it is a reply from Earth . He sets about coordinating a worldwide triangulation in expectation of a replay . The broadcasters suggest that the noise is some kind of distress signal . The Doctor is setting up the triangulation . Taltalian has set up another recovery probe that won ' t be ready for another ten days . Cornish is not happy with that and orders him to speed up or find another capsule from another country . Taltalian says there is no capsule ready in the world . The noise is replayed , and the Doctor sets about collating the data . Liz receives some data from France which confirms that the signal is coming from London . The Brigadier gets UNIT to do a local triangulation , which places it as emanating from an abandoned warehouse seven miles from where they are . Two men are sending a message from the warehouse . The UNIT forces arrive outside the warehouse . The two men stop the signal and wait for a response . They know they will be being monitored but hope they won ' t be tracked . An associate of theirs called the Sergeant enters and says that UNIT forces have arrived . He is ordered to stall them but only kill if necessary . A group of people , led by the Sergeant , hide from UNIT . The Sergeant fires his gun . The two men send the signal again , confident that the Sergeant will hold them off . The Sergeant kills one of the UNIT soldiers , and a fire fight ensues . Many are killed as some of the Sergeant ' s associates join in . It soon becomes a hand to hand battle . The Brigadier stops the Sergeant from escaping . They face each other , both pointing their guns at one another . A UNIT soldier approaches from behind the Sergeant and swings a heavy metal implement attached to the ceiling . The Sergeant dodges it , and the Brigadier is disarmed . The Sergeant has a clean shot of the Brigadier . Instead , he drops his gun and is led away . The two men trigger the self destruct function on the machine they have been using . The men go through the window , but not before they draw the Brigadier in by firing their gun . As the Brigadier enters , the communication device explodes . The Doctor complains to Cornish that Taltalian is refusing him use of his computers . Cornish contacts Taltalian and orders him to comply with the Doctor . Cornish is told by Athens that a solar flare is heading directly for where the probe is in orbit . Their controls are locked on manual , and there is nothing that can be done . He contacts them , imploring them to unlock the manual setting . On " Mars Probe 7 " , Cornish ' s pleas echo round an empty cockpit . The Doctor and Liz enter the computer suite only for Taltalian to emerge from behind the door and pull a gun on them . Episode 2 . Doctor Taltalian wants the tape . The Doctor asks if he understood the message , and Taltalian says he did . The Doctor holds the tape out to Taltalian only to make it disappear . Taltalian searches the Doctor for it but is interrupted by the entrance of the Brigadier . Panicked , Taltalian takes Liz hostage until he can escape . The Brigadier pursues . The Doctor makes the tape reappear and explains to Liz that he transmigrated it but won ' t explain how . The Doctor and Liz find the analogue to digital converter . The Brigadier returns and says that Taltalian escaped . The Brigadier tells the Doctor about what happened at the warehouse and says they have taken prisoners . The Doctor wishes to talk to them . The Doctor and the Brigadier interrogate the Sergeant , but he won ' t talk . The Brigadier asks him why he didn ' t shoot him when he had the chance . The Doctor suggests he was ordered not to . The Brigadier tells the Doctor that they have no knowledge of the Sergeant — even the labels of his clothes have been removed . The Doctor realises that they are dealing with something larger than the Sergeant and goes to leave . Before he does , he asks the Sergeant nicely if there is anything he can get for him before screaming at him like an army officer . The Sergeant springs to attention . The Doctor tells the Brigadier that the Sergeant is an army officer of some kind . A scientist comes to get the Doctor . The TV broadcaster informs the public that the two capsules have separated , but there is still no communication from either of the vessels . The Doctor and the Brigadier return to be told that the vessels are seven miles apart and expanding . The recovery shuttle is heading towards Earth and is eleven minutes from re - entry . They are all surprised when the shuttle starts its re - entry early . The Doctor leaves to check on Liz . The Brigadier leaves to run a security report on the Sergeant . Unbeknownst to the Brigadier , an anonymous figure disarms a UNIT soldier and frees the Sergeant . Liz and another scientist called Dobson have found no pattern to the tape . The Doctor suggests there might be something wrong with the computer . Dobson is sceptical , saying that the computer is infallible . The Doctor gets Liz to ask the computer what two plus two is . The computer responds with five . The Doctor says that Taltalian has sabotaged the computer . The recovery shuttle is ten seconds from control range . Contact is established between the shuttle and the Space Centre , but there is no response . The Brigadier is worried that the shuttle will burn up on re - entry . The Space Centre takes over control of the shuttle . Radar contact is made . The broadcast tells the public that the capsule is on course to land somewhere in the South of England . The Space Centre is tracking the capsule and controls its landing . Once it lands , the Brigadier and the Doctor congratulate Cornish . The Doctor , the Brigadier and Cornish go out to the capsule . Cornish speaks to the astronauts through a communication device on the outside of the shuttle . There is no response . Unbeknownst by them , they are being watched by the men from the warehouse . Cornish wonders if the astronauts are unconscious and also tells the Doctor and the Brigadier that the mechanism is jammed or locked and that they can ' t cut into the capsule as it would be dangerous for the astronauts . The Brigadier suggest they take the capsule back to the Space Centre . The Brigadier contacts UNIT headquarters and orders that the route is cleared between where the capsule landed and the Space Centre . He also asks for police outriders to accompany them . They load the capsule onto the back of a truck and head off . The Brigadier goes with the capsule in the truck , whilst the Doctor goes separately in Bessie . The Brigadier sees a helicopter in pursuit of the truck . It hovers over the truck and drops smoke grenade s , which disorientate the driver and the outriders . The truck is forced to stop . The helicopter lands . A firefight ensues between the UNIT soldiers and the men in the helicopter , who have alien weapons . Many UNIT soldiers are killed . One of the men takes off with the helicopter , whilst two others , the ones from the warehouse , steal the truck . The Doctor comes across the truck . He blocks the way with Bessie . The two men ask him to move , but the Doctor takes on the role of a doddery old man whose car has broken down . He asks for their help in moving the car . The men get out and push Bessie to the side of the road . As they do , the Doctor flocks an anti - thief device switch on the dashboard of the car , which causes the outside of the car to become magnetised and glues the men to the car . The Doctor re - steals the truck . The Brigadier is complaining to Cornish about the theft of the truck . He is flabbergasted to round the corner and see the recovery capsule being examined . The Doctor appears and explains what happened . He receives a phone call from Liz to say she has discovered the pattern . The Doctor leaves . Cornish continues connecting equipment to the capsule . Liz shows the Doctor the pattern she discovered . It proves that Taltalian has some kind of prior information regarding the situation . The Doctor heads off , saying that he is going to go and talk to the " top man " . Once alone , Dobson rings someone and informs them that the code is close to being cracked . The Doctor and the Brigadier explain to Sir James , the Minister for Technology , everything that has happened and their theory that there is a mole . Sir James seems blasé and sends the two men away . The Doctor is cross , but the Brigadier shuts him up . When the Doctor and the Brigadier leave , he goes to his cupboard where Taltalian has been hidden . There is no response from " Recovery 7 " . Cornish is preparing the thermal lances when Liz starts picking up some static . Sir James and Taltalian discuss how the Doctor is getting closer to their secret . Sir James say they are soon going to get a surprise . A voice comes from the shuttle . It is one of the astronauts asking for permission for re - entry . Cornish proudly tells them they are back at the Space Centre . The astronaut repeats his message for re - entry . He continues to repeat this message no matter what he is asked . The Doctor asks them to cut open the capsule . Episode 3 . The craft is opened and found to be empty , save for a recording of the astronaut ' s voices and a high amount of radiation . Carrington has ensured the contents — three space suited astronauts — are detained elsewhere , feeding them radiation to keep them alive . Carrington is now introduced to the Doctor by Sir James Quinlan , the Minister for Technology , who explains that he is head of the newly formed Space Security Department and that his actions were to protect the astronauts as they had been infected with contagious radiation . Quinlan states that they did not want the public to become panic - stricken , so Carrington had been acting with authority in his actions . By the time Carrington takes the Doctor and his friends to meet the astronauts , the situation has changed again . A criminal named Reegan has organised their abduction , killing the soldiers and scientists protecting them . Two of his henchmen are ordered to protect the astronauts , but the radiation they emit later kills them . Reegan , suited in protective clothes , disposes of their irradiated bodies in a Hertfordshire gravel pit , burying them under the rocks . He then returns to his laundry van . Covering his tracks with camouflage tactics , he pushes a dashboard button that flips over the van ' s number plate to another registration code . At the same time , the " Hayhoe Launderers Ltd " signage on the van changes to read " Silcock Bakeries " . Later on , the worker manning the industrial shovel uncovers the bodies when sifting the gravel . When the Doctor and Liz examine the situation , they work out that human tissue could not have withstood the degree of radiation emitted to the astronauts , who are still in orbit , meaning the three space suits contain alien beings instead . Reegan and his own scientist , Lennox , a disgraced Cambridge professor , are keeping the aliens alive , thinking the radiation needs to disperse , but they are weakening . Reegan enters their locked chamber to check up on one that collapses , but the alien recovers , thrusts him into a wall , and attempts to escape . Lennox flees , running up to find the laboratory exit locked , nearly getting him killed by the advancing alien . It runs out of strength again and falls down the stairs before laying a hand on him . Reegan recovers from the attack , disregarding Lennox ' s anger about locking the door . They realise the aliens need radiation to survive and begin dosing them with isotopes . In order to aid Lennox in maintaining the alien beings while they are incarcerated , Reegan lures Liz and the Doctor into the open by issuing a false announcement that the Brigadier wants them to examine the bodies of the radiation victims now uncovered in the gravel pit . The Doctor chooses not to go , wanting to ready " Recovery 7 " for another flight into space rather than wait for " Recovery 8 " , as its radiation has dissipated . Soon after Liz departs , the Brigadier walks in unexpectedly , and the Doctor learns he didn ' t send for them . Lethbridge - Stewart immediately gets after Liz , who is now on her way to Hertfordshire in Bessie . Another car staked out on a side road waits for her to pass , then takes chase from behind , and Liz fights to stay ahead of it . However , the horsepower of the modern vehicle quickly outpaces the vintage car and overtakes Bessie on a straight patch of road . Liz is forced to stop and bail out in a sprint , where Reegan ' s henchmen attempt to capture her . The chase leads to a pier , where Liz fights off one man but slips over a railing as another man grabs her by the legs , and she dangles helplessly above a death drop . Episode 4 . Despite Liz hanging off the edge of the bridge , she does not evade her captors and is brought to the lab where the astronauts are being kept to help Lennox . Carrington has issued a police alert for the return of Liz . He has also found some documents in a foreign language in the lab that , he thinks , proves that the astronauts have been stolen by a foreign country to be used as a weapon . The Doctor thinks that this is a plant and that the astronauts are still in space . He wants to decipher the impulses sent originally . Carrington says it is futile , but that does not put the Doctor off . Cornish and Taltalian are calculating how to get the capsule into space and are having to cut corners because of the blocks that Sir James is putting into place . The Doctor enters , and he and Taltalian make up . Cornish asks after Liz , and the Doctor says there is no news . The phone rings . It is for the Doctor . He is told that unless he stops interfering Liz will be killed . He hangs up and continues to decode the message . Liz is helping Lennox . Lennox sends a guard out to tell Reegan there is only one canister left . Whilst the guard ' s back is turned , Liz tries to run , but the door is locked . When she returns , she is scornful of Lennox ' s involvement in the project . He says he has nowhere else to go . As Lennox prepare to enter the quarantine , he hands Liz a key and tells her to lock him in the quarantine and run . She does so . The Doctor has cracked the code . It is instructions to build an electronic device . He questions Taltalian and says he is still an informer . Liz sneaks out and runs through the forest . Taltalian is shocked that the Doctor has accused him . The Doctor says that he can either confess to him , or he can be interrogated by the Brigadier . He leaves to build the machine . Left alone , Taltalian picks up a device and leaves . Liz attempts to hitchhike . A car pulls over . It is Taltalian . He pulls a gun on her and tells her to get in . She is returned to the lab , where she tells Reegan that the door was left open . Taltalian hands the device over to Reegan , saying that the creatures will respond to the commands that are given to them , and if they don ' t , they can threaten to cut off their radiation . Taltalian says that Reegan is to conduct a series of raids on targets . Taltalian berates Reegan for calling the Doctor , saying that it only got his ire up and that he needs to put out of way before he constructs another one of the machines . Reegan says he will deal with it . The Doctor tells the Brigadier about his suspicions regarding Taltalian , but he has no proof . The Brigadier is unsure , but the Doctor says he doesn ' t believe any of it . The Doctor requests a list of equipment and leaves , not before asking of any news regarding Liz . Lennox surreptitiously thanks Liz for not grassing on him . Liz is determined to escape again . In another room , Taltalian is anxious to return . Reegan gives Taltalian a bomb with which to kill the Doctor . He sets it for fifteen minutes but , while Taltalian ' s back is turned , changes it so it will explode straight away . Cornish is frustrated . All available astronauts have been transferred by Sir James . The Doctor volunteers to pilot the capsule . Cornish questions whether he has the ability to do so . The Doctor says he has spent more time in space than all of his astronauts put together and can face any tests required . Taltalian returns , and Cornish asks if he has the computations for the capsule left . Taltalian stalls him , and Cornish leaves . The Doctor asks if he has thought of the deal he offered him . Taltalian says he will tell the Doctor everything if he allows him to get away . He says he needs to go to his car for the information . He sets the bomb , which explodes instantly . The device that Taltalian gave Reegan can control the astronauts . The Brigadier and the Doctor pick through the debris in the lab . Taltalian is dead , betrayed by whoever gave him the bomb . The Doctor finds another one of the controllers in Taltalian ' s possession . Sir James tells Carrington that he has done everything to block Cornish ' s flight , but he can ' t delay anymore . Sir James suggest they tell the truth , but Carrington says they cannot do that , despite the launch of the capsule leading to a disaster for the entire world . Reegan shares his disappointment at the survival of the Doctor with a superior on the phone . Once he is off , he calls for a van and says that the astronauts are going on an excursion . Reegan asks Liz if the controllers can go the other way and if the astronauts can communicate with them . Liz says that it is possible , but something would have to be created . Later , an astronaut approaches a military base . A guard orders it to stop , but it continues . The guard fires at the astronaut , but it continues . The astronaut radiates the fence and kills the guard . The astronaut continues on and enters a workstation where he kills all the workers . He starts to search the workstation . A guard enters with a machine gun . The astronaut kills him . The Doctor has discovered that the device translates alien impulses into human speech and wants to build the other part of the machine . The Brigadier says he is trying to deliver as much equipment as possible , but they are coming from Japan . The phone rings . It is Sir James for the Doctor . He asks if the Doctor can be dissuaded from piloting the capsule . The Doctor says only if he is told the truth . The Doctor agrees , and he and the Brigadier make their way to Sir James . The astronaut enters Sir James ' office . He is killed . The astronaut uses radiation to open the safe and destroys the contents . The Doctor enters and only sees Sir James dead . As he checks him over , the astronaut approaches the Doctor from behind . Episode 5 . As the astronaut bears down on the Doctor , the Brigadier enters and shoots at it . The astronaut turns and rounds on the Brigadier . The astronaut escapes , killing a UNIT soldier as it leaves . It radiates the lock behind it as it goes , locking them in . Liz speculates that the astronauts are not human and questions Lennox as to whether Reegan is in charge . Lennox tells her that Reegan answers to someone higher up . Liz tells Lennox she has a plan for him to escape . The Brigadier shows the Doctor the bullets he fired at the astronaut . They are dented . The Doctor says they have been deflected off a kind of force field . A UNIT soldier says that there are strong traces of radiation leading outside the building and then it disappears . The Brigadier says this is proof that the astronaut was collected by a vehicle . The Brigadier wonders what the purpose of all this is and speculates if it is conquest . The Doctor states that this is what they are supposed to think . The astronaut is returned to the lab . Cornish is explaining the capsule to the Doctor . He explains that , due to the blocks already established before Sir James ' death , they have had to mix standard fuel with a type of fuel named M3 which has never been done before . The Doctor ' s medical report is presented to Cornish . He seems confused by it , but the Doctor swiftly moves on . The astronaut collapses as soon as it is back in the quarantine . Lennox re - radiates it . Liz asks Reegan what it has been doing . Reegan explains it has been killing her UNIT friends . When he leaves , Liz accuses Lennox of facilitating murder . Liz says that Lennox should go to the Brigadier and that she can help him talk his way out . Carrington enters the Space Centre and tries to block the launch of the capsule . Cornish points out he does not have the rank to do that . Carrington says he is convinced that this is an alien invasion with the collaboration of a foreign power . The Doctor points out that this does not explain why he opposes it . Carrington says that he believes the capsule should carry a nuclear warhead instead . Carrington says he is going to take his objections to the highest level . Cornish says that he had better hurry as they will be launching in two hours . The astronaut is recovering . Liz and Lennox are still squabbling . Liz tells Lennox to tell the guard he needs more isotopes and that he needs to see Reegan . Lennox tries this but is blocked . Liz fabricates a story about the astronauts dying and convinces the guard . He still does not let Lennox leave , but Liz convinces him that the death of the astronauts will be on his hands . Lennox also adds that he is not a prisoner . The guard is convinced and frees Lennox . The capsule is ready , and the Doctor is summoned to the preparation room . The Brigadier asks the Doctor why the launch time has been brought forward . The Doctor explains it has been done to thwart Carrington . There is a call for the Brigadier . It is Sergeant Benton , who says that a man named Lennox is desperate to see him and is frightened out of his wits . The Brigadier tells Benton to put him in a cell until he has a chance to speak with him . Lennox is led to the cell and is unsure of its safety . He implores the guard to lock the door . The Doctor is ready for the launch . The Brigadier says goodbye , and the Doctor proceeds to the capsule . Reegan is cross at the guard for letting Lennox go . The guard blames Liz . Reegan grabs her and puts his gun to her head , demanding to know where he went . Liz says he went to the Brigadier . Reegan rushes to the phone and calls someone . He says that they are to take care of Lennox while he will take care of the Doctor . Cornish is performing an instrument check on the capsule . The Doctor is very impatient and only gets more so when told he is still thirty - three minutes away from launch . He is told that the fuel is taking a long time to load and that they have to get the balance between standard and M3 fuel just right , otherwise the ship will blow up in orbit . A man tries to infiltrate the Space Centre dressed as a mechanic . He knocks a guard unconscious and begins to climb the scaffolding around the launch site . He kicks a worker that tries to stop him off the side . He begins to turn valves around the launch pad . A fuel injection malfunction registers in the Space Centre . Cornish is concerned , but it soon self rectifies . The man is still making his way around the launch pad , knocking out any workers that he comes across . He turns a large valve on a cylinder marked " M3 Fuel " . He climbs higher and higher , turning valves as he goes , and then makes his escape . Food is brought to Lennox . As the guard leaves , he implores for the door to be locked . He takes the lid off his food and finds an isotope . Horrified , he presses the panic button , but there is no response . The Brigadier finds the groggy soldier whom the saboteur knocked out . He rushes out and investigates , seeing the damage he has left . At the Space Centre , they are all set for take off . The countdown begins when the Brigadier rushes in and orders the take - off to be cancelled . Cornish ignore him and the rocket takes off . The Doctor is sustaining huge amounts of G force and the rocket ' s speed is 20 % higher than it should be . The fuel burn will not reduce , and the Doctor is at risk of blowing himself out of Earth ' s orbit and into the Sun . Cornish implores the Doctor to try to control the fuel burn manually , but the heat has corrupted the controls . The rocket ' s speed is now 37 % higher than it should be . The Doctor tells Cornish to jettison stage one of the rocket , but Cornish is reluctant to as it will mean the Doctor would struggle to get into orbit . The Doctor points out that it is the only option they have . Cornish orders the jettison . This stabilises the rocket and returns the speed to normal . The Doctor is informed of the saboteur . Later Cornish is directing a very casual Doctor towards " Mars Probe Seven " . The Doctor links the capsule to the probe and unbuckles himself , ready to move into the probe . Cornish urges caution , but the Doctor is calm . As he opens the hatch , Cornish warns of a UFO in collision with the Doctor and orders evasive action . The Doctor looks out the window and sees a large red disc approaching him . Episode 6 . The red disc is a spaceship . The Doctor tries to evade it , but he doesn ' t have enough speed as he is still linked to " Mars Probe Seven " . The Space Centre loses communication with him . It has collided with the ship . The capsule must be smashed to fragments . The Doctor awakes inside his capsule . A voice tells him that he is not in danger and that he can leave his capsule . He is told he doesn ' t need his space suit as an environment has been prepared for him . He asks where the astronauts are . He is told they are unharmed . He walks out into a large red tunnel . He is told to walk into the light . He finds the astronauts watching a game on a screen . They are in good spirits . They are under the assumption that they are in extended quarantine on Earth . The Doctor tells them the truth , and they don ' t believe him . A noise hypnotises the astronauts . A figure emerges from behind a screen . It explains that the astronauts have had their mind conditioned so as to stop their mind deteriorating . The figure says that Earth has not returned their ambassadors and , unless they are returned , they will destroy their world . The Space Centre have discovered that the ship is half a mile in diameter . Carrington wants to attack and destroy the ship . The Brigadier says they cannot do that with the Doctor on board , but Carrington says he is most likely dead anyway . Carrington leaves for Geneva to push for an all out attack . The Brigadier shocks Cornish when he seems to be somewhat on the side of Carrington , but the Brigadier also thinks that Carrington has more information than he is letting on . Their only hope is the Doctor . The Doctor says that the authorities on Earth have no knowledge of the ambassadors . The alien figure says it finds that hard to believe . The Doctor asks to go back and return the ambassadors . The alien agrees but echoes his threat . The Doctor asks if the astronauts can come with him , but the alien says that they are to remain as hostages . The astronauts return to consciousness , and the Doctor leaves them in blissful ignorance that they are in quarantine . The Space Centre learns that NASA are launching an observation satellite to monitor the spaceship due to the fact that it is emitting radio signals . The Brigadier tells Cornish of the murder of Lennox . Cornish is starting to question UNIT ' s efficiency . The Brigadier lists what has been discovered already . The bodies in the gravel pit belonged to petty criminals , the bomb that killed Taltalian was an experimental bomb being refined by the army and not for general use yet , there was insecticide on Lennox ' s shoe that they are tracking to local countryside and the isotope used to kill him was sold to a company that no longer exists . Cornish takes back his questioning of UNIT ' s ability . The Space Centre is alerted that the radio signals have stopped . The Doctor returns on the video screen . He says that the astronauts are safe and well , but he can ' t say anymore as it is not safe . He explains he is going to land and that UNIT ' s men should be on standby . The Doctor breaks communication and starts re - entry . Liz is radiating the ambassadors when one of them stops her from leaving . It lifts up its helmet to reveal an alien face . Terrified , she escapes . She shows Reegan , who seems nonplussed . He tells Liz of the death of Lennox and offers her his job . The phone rings . Reegan is told that the Doctor is returning from space and that he is to be killed . Reegan sets off . The Doctor is four and a half minutes from touchdown . The Brigadier wants to go and meet him , but Cornish tells him it will take him an hour to get through decontamination . A lorry approaches the Space Centre . Reegan is driving and produces some papers . He is waved through . The Doctor has landed . The lorry draws up at the decontamination unit ventilation system . Reegan sets about fiddling with pipes and gauges . The Doctor enters the decontamination unit . Reegan puts a gas canister onto one of the pipes . The Doctor is told that they are awaiting the test results and that he has to stay in the decontamination unit longer . He lies down . A gas starts to enter through a vent , and he starts coughing . He tries to rise up but falls to the ground . Reegan stops the gas and enters the decontamination unit wearing a gas mask . He picks the Doctor up and drags him out . Cornish is told that all the tests are negative and tells the Doctor that he can leave decontamination . There is no response . The Brigadier rushes off to investigate . The lorry drives away . The Brigadier enters and discovers the gas and the Doctor gone . He tells Cornish and orders the gates sealed , but it is too late ; the lorry has already left . The Brigadier reports the abduction of the Doctor . Carrington thinks it is a blind and that the Doctor is working with the aliens . He questions the Brigadier about how much he knows about the Doctor . Carrington says he is going to investigate the Doctor and then blast the spaceship out the sky . Reegan tells his superior that the Doctor is dead , but it is not true . The Doctor comes to and is reunited with Liz . He investigates the ambassadors and tells Reegan what he saw . When Reegan asks how he communicated with them , the Doctor says they have a translation device . Reegan shows the Doctor the one that Taltalian gave him , and the Doctor states it is far more complex than that . Reegan asks if the Doctor can build one ; he says that he can , but he won ' t . Reegan says he will kill him unless he does . The Doctor sits down to make a list of the equipment he ' d need . Reegan leaves them . The Doctor tries to escape , but Reegan is loitering by the door . Liz tells the Doctor about her failed escape . The Doctor sits at the desk and starts making the list , telling Liz that if they can ' t get to the Brigadier , maybe his list might bring the Brigadier to them . Carrington enters , armed . Carrington reveals himself to be Reegan ' s superior , and seeing as Reegan didn ' t follow his orders and kill him , he will have to do it himself . Episode 7 . Reegan enters and begins to squabble with Carrington . He says he kept the Doctor alive as he is the only man who can create the machine that will help them communicate with the aliens . Carrington realises that Reegan is alive . The Doctor questions Carrington as to what his plan is . He says he wants to alert the world to the menace of the aliens . The Doctor says he knows that these aliens seek no ill will . Carrington is convinced that they are hostile and tells a story of how he first encountered them on Mars , where they killed one of his fellow astronauts . The Doctor states that they probably didn ' t know they were radioactive and wouldn ' t have intended to harm . Carrington will not be dissuaded and says that they have walked into his trap whereby he will convince the world they are evil . He says that he is the only one who knows of this plan and that no one else has helped him . The Doctor agrees to continue making the machine . Carrington tells Reegan that he wants to take an alien with him . NASA ' s satellite is within three miles of the UFO and drawing in . Carrington orders Reegan to raid an isotope store with the aliens . The Space Centre receive news that there is no signal from the satellite and that it has disintegrated . The Brigadier receives a phone call from Carrington , who tells him he has captured one of the astronauts and is bringing it to the Space Centre . Reegan implores the Doctor to be quicker in the construction of the machine . He takes the aliens away with him , despite the Doctor trying to convince him otherwise . Reegan says he wants the machine finished on his return . The Doctor continues construction of the machine , much to Liz ' s surprise . The van draws up to the isotope store . The ambassadors leave the van and break through the fence , radiating a guard . The alarm is raised . The van enters . Carrington is preparing a live video cast wherein the alien is going to be revealed . The presenter , Wakefield , questions if this is not going to raise a panic . Reegan sets about stealing isotopes . The police rush to the scene as Reegan is loading them onto the van . The ambassadors radiate the policemen but do not kill them . The Brigadier tells Carrington of the isotope robbery . Carrington says that this proves that the aliens are dangerous , and the fact that they are accompanied by men proves that there are traitors in their midst . Again , he accuses the Doctor of being in league with the aliens . He tells the Brigadier that he will tell the world to unite against the aliens on his broadcast . The ambassadors are back in quarantine . The Doctor has finished his machine and is about to test it . Conspiratorially , Liz asks if the signal is strong enough . The Doctor begins to tap Morse code whilst pretending the machine isn ' t working . The Doctor ' s Morse code is being picked up by all number of different radio receivers , including UNIT . They set about triangulating the signal . Wakefield and Carrington are going through a dress rehearsal of the broadcast . Cornish talks to Wakefield and tries to persuade him to not broadcast . Reegan questions the Doctor about what is taking so long . The Doctor says he is ready to test . He tries to talk to the ambassadors . There is no reply . He tries again . Again , no reply . The third time the ambassadors turn and ask why they are being kept prisoner and why they are being used to kill . Reegan snatches the microphone away from the Doctor and threatens the ambassadors . If they do not do what he says , they will be left to die . The UFO communicates with the Space Centre . They are told they have little time to return their ambassadors before they turn all their powers against Earth . Carrington says they must now attack and that he needs to broadcast immediately . Wakefield says he can ' t for another hour , and Carrington tells him to hurry . Cornish tries to dissuade again , but it falls on deaf ears . The Brigadier tells Carrington of the SOS signal being picked up , and he suspects it is the Doctor . Panicked , Carrington has the Brigadier arrested , saying that he too is in league with the aliens . The Brigadier is told that all his UNIT men have been arrested and replaced with men loyal to him . Cornish tries to ring the ministry , but Carrington says he has cut communication and is now in charge of the Space Centre . The Brigadier disarms the guards and steals a car , managing to escape from the Space Centre before the alert is raised . He arrives at the radio communication centre where they have triangulated the signal to a disused firing range not far from the Space Centre . The Brigadier starts to see Carrington ' s hand in all of this . He is told there is only one mode of transport to get to the firing range — Bessie . The soldiers pile in and reach the firing range . They arrive as some men leave , and a fire fight ensues . The men run out of bullets and , seemingly , surrender , but as they draw near a fist fight breaks out . One man is shot whilst the Brigadier throws another off the edge of the cliff . Inside , Reegan is trying to convince the Doctor to work alongside him . They hear the gun shots and the Brigadier enters , shooting the guard and injuring Reegan . He explains Carrington ' s plan to the Doctor . Reegan suggests they could use the ambassadors as a way of getting back into the Space Centre . The Doctor explains the plan to the ambassadors . Bessie and the van draw up to the entrance of the Space Centre . The Brigadier asks the men to open the gates , but they refuse . The ambassadors are let free . The Doctor tells them to open the gates and to try not to harm anyone . The soldiers shoot at the ambassadors , to no avail . The Doctor warns the soldiers of the ambassadors ' powers . They back off , the ambassadors open the gates and Bessie and the van drive in . Carrington and Wakefield are still going through the dress rehearsal . Cornish implores with Carrington again , and Carrington has Cornish taken away by security . They are five seconds from broadcast . As Wakefield introduces Carrington , a banging is hear and then screams . The ambassadors enter , followed by the Doctor , the Brigadier and the UNIT soldiers . The Brigadier arrests Carrington . As he is led away , he tells the Doctor that he had to do what he did . The Doctor releases the ambassador that Carrington had trapped and says a message needs to be sent to the UFO . Cornish asks after his astronauts , and the Doctor says that they are safe . All that needs to be done is send the ambassadors up in " Mars Probe Seven " and exchange them for the astronauts . Even the issue of fuel isn ' t a problem . The ambassadors are immune to g - force so they can use the M3 variant . The Doctor bids Cornish farewell . Liz is to stay in and help with the exchange . As he leaves , the Doctor goes to shake the ambassadors ' hands before thinking better of it and wishing them a nice trip . Home video and audio releases . DVD . Originally planned for DVD release in 2011 alongside " The Sun Makers " , " The Ambassadors of Death " was delayed due to ongoing re - colourisation issues . These issues were resolved to the best of the Restoration Team ' s abilities in November 2011 . The serial was released on 1 October 2012 . The release is wholly in colour , with no option to see the parts that were monochromatic in the original VHS release . Digital releases . This story is available : VHS . This story was released on VHS in 2002 as a single selection , and in 2003 in the United States as part of the " End of the Universe " collection . The story was released with over 90 minutes of the story in colour , and the remaining material in black and white — with subtle mixes between the colour and monochrome sections . Episode one was taken from the original 625 line PAL colour videotape , episode four was black and white throughout , and episode five was a version with electronically restored colour . The remaining episodes were both colour and black and white . Editing for the VHS release was completed by Doctor Who Restoration Team and also contains a black and white version of the trailer for the story before episode one and " The Stages of the Restoration " , a mini - documentary about the restoration techniques , after the last episode . CD . A CD of the original television soundtrack was released in August 2009 , with linking narration by Caroline John . This was an unusual move for BBC Audio , since typically they released soundtracks only for those stories which had missing episode s . This is one of the very few stories which visually exists in its ( near ) entirety to also get an audio release .