Petronella Osgood Petronella Osgood was a scientist who worked for UNIT , acting in a capacity of a personal assistant to Kate Stewart , in the early 21st century . An admirer of the Doctor , she eventually met the Time Lord during the infiltration of UNIT by Zygon invaders , which was resolved by the Eleventh Doctor joined by his tenth and war incarnations . ( TV : " The Day of the Doctor " ) The original Osgood and her Zygon double became indistinguishable from each other to everyone else . They refused to identify which one of them was Zygon and which was human . ( TV : " The Zygon Invasion " ) One of them was killed by . ( TV : " Death in Heaven " ) After a Zygon rebellion was ended peacefully , the Zygon rebel leader Bonnie took on the form of Osgood to maintain the peace . Both Osgoods still refused to identify if she was the human or Zygon version but promised to identify if she was human or Zygon one day when no one would care anymore . ( TV : " The Zygon Inversion " ) Biography . Osgood came from a family of science geeks . ( AUDIO : " Earthfall " ) She was recruited into UNIT because of family connections . ( AUDIO : " Power Cell " ) She had a sister . ( TV : " The Day of the Doctor " ) Joining UNIT . Osgood often created pieces of technology to aid in UNIT ' s missions , typically to stop the soldiers from shooting at aliens , much to Kate Stewart ' s delight . She tracked a set of energy units falling to Earth and warned Vikram Shindi about it . ( AUDIO : " Vanguard " ) Together with Lieutenant Sam Bishop , she was deployed to the Gobi Desert in Mongolia in search of a Nestene energy unit . She had created a holographic image projector from alien technology . ( AUDIO : " Earthfall " ) She tried to examine the energy unit using all the techniques she could think of . Kate also told her to examine one of the 3D printers . When the Nestene escaped the energy unit , she discovered that the Nestene could combine through the internet . ( AUDIO : " Bridgehead " ) She created a new weapon to destroy the Auton s and was able to free Captain Josh Carter from Nestene control . ( AUDIO : " Armageddon " ) Meeting the Doctor . She was present when the TARDIS , with the Eleventh Doctor and Clara Oswald inside were brought to the National Gallery in an effort to understand what had happened to several paintings in the Under - Gallery . The Doctor took a liking to her long multi - coloured scarf , which was strikingly similar to one he wore in his fourth incarnation . She displayed a type of hero - worship belief in the Doctor , twice " praying " to him to save her during moments of danger . On the Doctor ' s orders , she and fellow scientist McGillop analysed the stone dust in the Under - Gallery and eventually realised that the dust on the floor was the remains of the statues , which had been smashed by Zygon s that had escaped from the paintings in order to hide . She was able to escape from them , although she was duplicated by one of their number before she got away . She was asthmatic , and often forgot to use her inhaler when needed , especially when over - excited , often being reminded by Kate when she started wheezing . The Zygon who took her form disliked this , annoyed at " getting one with a defect , " and promptly took her inhaler . When she escaped from this Zygon by tripping it with her scarf , she reclaimed her inhaler . Osgood was in the Black Archive with her Zygon version when Kate threatened to destroy London , rather than let the alien technology in the archive fall into Zygon hands . Like the other human s and Zygons in the room , her memory was temporarily cleared by three incarnations of the Doctor , so that she could not recall whether she was the real Osgood or her Zygon duplicate . As peace talks ensued , she realised who the real Osgood was when the Zygon duplicate began wheezing and did not have the inhaler . She gave it to the Zygon version , and both Osgoods agreed to keep their discovery a secret so as not to disrupt the peace talks . ( TV : " The Day of the Doctor " ) Tengobushi Incident . After going to a pub quiz with Jay Roy , she was tasked working out which pieces of UNIT property Lyme Industries had managed to get their hands on . She later asked Jay to help her in her work in order to work out what was kidnapping people . She started to show Jay the ropes but didn ' t get too far when a Tengobushi attacked . Jay decided to protect her and detonatd a bomb in her flat killing himself in the process . ( AUDIO : " Power Cell " ) When she went to Geneva she decided to visit local Galleries , and she was followed and attacked by Dokan . She later went with Kate and Grant Avery to investigate a set of murders on a French mountainside . Going back to Geneva to analyse some secretions but was attacked by the Tengabushi but was save by Josh . She realised that the Tengabushi wanted her for her knowledge of an Alien artefact and used this to get into their ship . ( AUDIO : " Death in Geneva " ) She and Kate had to fly their plane after the Tengobushi killed the pilots . She then investigated the Kamishi energy cell in the surroundings of the Black Archive . As part of her experiments she accidentally released some power that caused some earth tremors . After the Tengobushi released an energy barrier around the Tower , she released the Raven ' s to observe their advance . During the attack she was trapped in the Archive , Josh managed to get her away but managed to get her first to the Jewellery room and then to command centre . She managed to work out how to use the energy cell , and weaponised it to aid their escape . ( AUDIO : " The Battle of the Tower " ) When they were under lock and key under Peter Latcham ' s orders in UNIT ' s base under the Rock of Gibraltar , she managed to hack into the bases computer to get their release . Whilst at Lyme ' s base in Antarctica she worked out a way to destroy the generator and destroyed it with the help of Dokan . The Kamishi questioned her about her actions . ( AUDIO : " Ice Station Alpha " ) Investigating the Silence . Osgood received a panicked call from Colonel Shindi who detected something near Helena Faversham ' s residence . While she was tracking the Silents she kept forgetting the positive readings , and after she was attacked by the Silents she soon forgot . She then questioned Faversham using a truth serum . ( AUDIO : " House of Silents " ) She was working on a universal translator which could understand Axon and Sontaran . She helped Bishop to discover what happened at the Faversham estate . She later worked out a simplistic way of remembering the Silents , by writing stuff down . Investigating the people that went to Faversham ' s home , She started with the ones closest to her but the all disappeared . She and Bishop tracked Derek Butler but he as snatched from under her nose . She then looked through all the videos the people she was looking for had made and found subliminal messages to get the UK population to trust Kenneth LeBlanc . ( AUDIO : " Square One " ) A month later she had to brief the rest of UNIT about her solution to getting the rest to remember the Silents . She had created a pair of sunglasses which had 360 degree cameras which could give them all views of the Silents . She called the Silents " Edvard " . After she stole Carter ' s laptop , using the same techniques the Silents used , she found a large order of guns and explosives he had ordered . She also used it on Heston to find out where he had taken the things Josh ordered . She then tried to stop Josh from killing LeBlanc but couldn ' t so knocked him out . ( AUDIO : " Silent Majority " ) She went with Bishop to the UNIT satellite to fix something on there , but they were knocked unconscious upon arrival . She started to explore the space station and found a Silent on - board . They were being controlled by the Silents and exposed the spy satellites of all the governments of the world . She tried to get the Telokni ship to stop shooting them but couldn ' t and had to escape . ( AUDIO : " In Memory Alone " ) The Sillurian invasion . Osgood was investigating an Silurian nest near Scafell when they started to attack . She managed to escape to John Benton ' s pub . She tried to contact UNIT HQ but barely got a message through to Josh . Noticing that the Silurian ' s retreated when Terry Waring ' s car blew up , she devised a plan to burn the beer cellar of the pub and create a back draft to halt the Silurian ' s progress . She then escaped in Bessie ( AUDIO : " Call to Arms " ) She was sent with Jo Jones to invesitage ' Project Charybdis ' . Whilst there it was hijacked by Anthony Burmaster to get the a Sea Devil base . Before the Project was exploded she managed to escape . When Jo decided that she should continue the Doctor ' s work she got Jo to the Sea Devil base . She later stopped Kate from destroying the Sea Devil base by noticing that the tremor wasn ' t a weapon but the base collapsing . ( AUDIO : " Tidal Wave " ) She went with Kate to a Silurian Nest in Greece whilst there she met some dormant dinosaurs . In the nest she was looking for a device to control Krellix ' s hybrids . Tryska used a machine that induced fear into her and she relived race memories of the Silurians , and started to run round the base . Sam later found her covered in a liquid and regressed to a primitive state . But in that state she found a way to stop Tryska before the base blew up . ( AUDIO : " Retrieval " ) She realised that the Silurians must have breeding programme for Dinosaurs for millennia . Managing to get to London , she got to her labs to find a way of disarming the Silurians ' and not killing them . Jo started to help her in the work . She eventually found a possible solution , of stopping the dinosaurs the Silurians ' rode . She was able to disarm the nuclear weapons that Kalana had armed . After the defeat she went with Jo and Sam to South America in order to return the Sea Creatures back the Sea Devil base . ( AUDIO : " United " ) Brief Encounters . She and the team flew to South America on intelligence that a local resistance force had obtained alien technology . There they met resistance leader Captain Gonsalves and discovered she had a captured Dalek in her secure bunker . While Kate and Shindi searched the jungle for possible other Daleks , Osgood and Josh searched the base . They discovered a series of rooms containing human weapons augmented by alien technology and were captured by Gonsalves . Held captive with Kate , in the bunker , they both discover Gonsalves was part of a worldwide auction house of alien technology and weapons . Having re - entered its casing the Dalek kills Gonsalves and self - destructs , destroying the bunker . Having escaped the explosion Osgood and the team were then rescued by the American arm of UNIT . ( AUDIO : " The Dalek Transaction " ) Working late in her lab , on Halloween , Osgood picked up a broadcast from an obsolete satellite called Voxtel , partially broadcasting in Latin . When Josh arrived back from a party saying he saw an apparition of a Grey Man , at the same time as the broadcast , Osgood believed the two were connected in some way . After hearing some unsettling messages from Kate , Josh persuaded Osgood to accompany him up to Ealdon House in a UNIT helicopter . Once there Osgood discovered the apparitions of the Grey Man were created by a particular resonance in the house , causing fear in humans . Alice Donelly had also discovered this resonance in the house years before and she wanted to harness it as a weapon before Kate ’ s father stopped her . Now with apparitions of the Grey Man appearing across London and an unknown alien presence drawing near , responding to the Voxtel message Alice left years ago , Osgood and Kate deciphered and completed the message , obverting the crisis . ( AUDIO : " Invocation " ) After attending the New Science Conference Osgood runs into an old mentor of hers ; Professor John Torrance . He persuades her to let him give her a lift home , or close to , but he ends up taking her to his workplace , the Torrance Research Foundation . There Osgood discovered Torrence and his colleague Christine Colley engaged in cloning research and is introduced to Max , a cloned Rhesus Macaque . She also discovered a captured Sontaran called Merx who had been experimented on so Torrence could clone a Sontaran army via his own methods . This army would then be sold off through Colley ’ s contacts in the worldwide auction . Confined together Osgood and Merx hatch a plan to escape but they are rescued by a combined force of Sontarans and UNIT . With the cloning project and the Foundation being shut down , Osgood takes Max to safety . ( AUDIO : " The Sontaran Project " ) Osgood and Josh became trapped in a sideways dimension after an experimental travel capsule took them there by mistake . Here UNIT was run by a fasist state with different versions of the team , including herself . She was startled to discover this world ’ s Osgood and Josh were , very much , an item and she had some trouble avoiding his advances . Unfortunately Josh was forced to leave with the evil Osgood but the capsule left behind a dimensional tare that non - evil Osgood used as a gateway to jump across to her reality . When she returned Josh without thinking planted a large kiss on her lips before realising his mistake . Soon the other Osgood attempted to escape again in the capsule . With its power levels approaching critical Osgood managed to persuade her other self to jump start the capsule just before the dimensional gateway imploded . Heading to Kate ’ s office this left the real Osgood and Josh ’ s relationship ambiguous . ( AUDIO : " False Negative " ) The two Osgoods . The two Osgoods created Operation Double , where a group of 20 million Zygons would be allowed to live on Earth and take on the form of the nearest person they could find . The treaty could only be maintained if both humans and Zygons agreed to live among each other in peace , and that no harm would come to anyone . They were given a device called the Osgood Box by the Doctor , only to be used only in a dire emergency . ( TV : " The Zygon Invasion " ) In 2014 , one of the Osgoods were sent to Bonnybridge to investigate another U . F . O . sighting in the area . Because of this , she missed the first known interaction between the Twelfth Doctor and UNIT as well as the Fracture s ' attack on London . ( COMIC : " The Fractures " ) After began to deploy her Cyberman army across the world , one of the Osgoods confronted and secured her . She was stationed near Missy during her captivity aboard Boat One , who told Osgood , " I ' m going to kill you in a minute , " calling it their secret girl plan . Missy proceeded to count down to Osgood ' s death , taunting her with each number . She then unlocked her handcuffs , killed her guards and grabbed hold of Osgood . Despite claiming to be more useful to Missy alive , Osgood was vaporised , with only her glasses remaining intact until Missy crushed them under her heel . The Twelfth Doctor later discovered them , crushed on the ground , and realised that Missy had murdered her . ( TV : " Death in Heaven " ) After the death of one of the Osgoods , the other one refused to state whether she was the Zygon or the human . She became a target of a revolt from a rogue group of Zygons who believed they had been betrayed . ( TV : " The Zygon Invasion " ) After the Doctor convinced Bonnie , the leader of the Zygon revolt , to stop her plan , Bonnie also assumed Osgood ' s form and acted as the second protector of Earth alongside the other surviving Osgood . She felt that they were a credit to both humans and Zygons and planned to take on the role of protecting the Earth from threats . ( TV : " The Zygon Inversion " ) In September 2015 , the two Osgoods watched prime minister Daniel Claremont ' s speech on global warming at Ravenscaur School with Kate Stewart in the Tower of London . After Claremont was revealed to be a Sea Devil during the speech , the Osgoods recommended that Kate call the Doctor . The Twelfth Doctor was already there and he defeated the Sea Devils without UNIT . ( COMIC : " Clara Oswald and the School of Death " ) In early 2016 , one of the Osgoods was in London when it was attacked by K2 . She called the Twelfth Doctor and he took her into his TARDIS . They materalised above the London Eye as it was attacked by the robot . The Doctor used his sonic screwdriver to destroy K2 , but he fell out of the TARDIS . Osgood saved him by throwing her scarf out of the TARDIS for the Doctor to catch . ( COMIC : " Robo Rampage " ) One Osgood mailed the other based on a large increase of transmitter activity coming from Saxon Heights . They realised that this was Missy and later had UNIT crash into the school . However Osgood later confirmed to Kate Stewart that they had lost her . ( PROSE : " Yes , Missy " ) One of the Osgoods was the commanding force behind UNIT ' s shutting down of Harmony Shoal , following an anonymous tip off . ( TV : " The Return of Doctor Mysterio " ) Personality . Osgood was a " fan " of the Doctor and knew of many of his previous incarnations . She would pick iconic items ( i . e . multi - coloured scarf , bow tie ) from the incarnations she knew of and wore them herself ( TV : " The Zygon Inversion " ) When asked by the Twelfth Doctor if she would like to travel with him , she was so excited that she had to use her inhaler . ( TV : " Death in Heaven " ) Osgood would become saddened if she learned she missed a chance to see the Doctor ; one of her fellow scientists even stated she would be disheartened to learn the Doctor had regenerated again after she had just started mimicking his previous self ' s fashion . ( COMIC : " The Fractures " ) Osgood was also very intelligent . She alone was able to work out the reason why the Zygons smashed the statues in the Under - Gallery . ( TV : " The Day of the Doctor " ) She also surprised the Twelfth Doctor by correctly presuming that Missy was the Master regenerated into female form : UNIT kept files on all past Prime Minister s , including the Master . ( TV : " Death in Heaven " ) She also came up with a hypothetical plan for invading Earth by killing the Doctor by shooting him between the eyes for each regeneration , never allowing him to talk . ( TV : " The Zygon Inversion " ) She managed to figure out whether she or her Zygon doppelganger was the real Osgood after the Tenth and Eleventh Doctor s , joined by the War Doctor , jumbled their minds , making them unable to determine their own species , in an attempt to facilitate negotiation of the ultimate peace treaty . She managed to determine this as her Zygon counterpart suffered an asthma attack , motivating her to pass her asthma inhaler to the other Osgood . ( TV : " The Day of the Doctor " ) Osgood had a sister to whom she negatively compared herself . ( TV : " The Day of the Doctor " ) Missy observed that she had little confidence in herself . Osgood was able to keep her cool , even when faced with the threat of death from Missy and tried to reason her way out . ( TV : " Death in Heaven " ) Appearance . Osgood dressed according to the Doctor ' s fashion senses from various incarnations , choosing to wear a similar scarf to that worn by the Fourth Doctor . ( TV : " The Day of the Doctor " , COMIC : " Robo Rampage " ) She later wore trainers similar to those worn by the Tenth Doctor and a bow - tie similar to that worn by the Eleventh Doctor and a leather jacket like the Ninth Doctor . ( TV : " Death in Heaven " ) She also wore a shirt with question marks on the collars , like the Fourth , Fifth and Sixth Doctor s , and a cardigan similar to the Seventh Doctor ' s . ( TV : " The Zygon Invasion " ) One at least one occasion she wore a costume inspired by the Sixth Doctor . ( COMIC : " The Lost Dimension " )