Toshiko Sato Toshiko " Tosh " Sato ( 1975 - 2009 ) applied her scientific skills to the Torchwood Three team , after having worked for the Ministry of Defence . Beautiful , brilliant and insecure , much of Tosh ' s private life remained mysterious even after her death . She lost her life after enduring severe blood loss from a gunshot inflicted by Gray , but before the wound claimed her life , she fought on long enough to help Owen Harper save Cardiff from a nuclear disaster , even though it cost him his life as well . Biography . Early life . Her logout screen gave a date of birth as 19 September 1981 , ( TV : " Exit Wounds " ) this was due to an incident she had whilst trying to stop a torrent file from corrupting the world ( torchwood _ cascade _ CDRip . tor ) but , Toshiko was really born in London in July 1975 . Her parents moved to Osaka , Japan , in 1977 , then back to the UK in 1986 . Her Japanese - born grandfather was a decoder at Bletchley Park and her parents were in the RAF . ( TV : " Greeks Bearing Gifts " ) She had a brother whose death she felt some responsibility for , feeling that she had abandoned him . ( AUDIO : " torchwood _ cascade _ CDRIP . tor " ) At a young age , Toshiko enjoyed being a member of Maths Club at her school . When she moved into her own flat , she didn ' t have a flat warming party as there was no one she wanted to invite . ( TV : " Adam " ) Later life . Around 2003 , ( TV : " Fragments " ) though possibly in 2005 , ( TV : " Greeks Bearing Gifts " ) Tosh worked at the Lodmoor Research Facility , run by the British Ministry of Defence . Blackmailed , with her mother ' s life at stake , Tosh stole plans to make a sonic modulator and successfully built one , even though the plans were faulty . She was arrested by UNIT and held indefinitely without trial , and then saved by Jack Harkness . He complimented her on making a functional model with only the schematics available and offered her a job with Torchwood as an alternative to spending the rest of her life in a UNIT holding cell . ( TV : " Fragments " ) Life with Torchwood . Every year for a day , Torchwood Three had woken up Tommy Brockless , a World War I soldier frozen in 1918 . During the four years Toshiko worked for Torchwood , she fell in love with him . ( TV : " To the Last Man " ) Toshiko was present in the Hub on 26 March 2005 when it was temporarily frozen in a time bubble for a day by Torchwood One ' s Rajesh Singh so that director Yvonne Hartman could procure a Drahvin scanner from the Hub unhindered . Observing the frozen Toshiko , Yvonne remarked that she was " cute " . ( AUDIO : " One Rule " ) While covering for teammate Owen Harper , who was suffering from a serious hangover , ( TV : " Exit Wounds " ) Tosh , pretending to be a medic named " Dr Sato " , performed an autopsy on the supposed pilot of a spaceship crash inside Albion Hospital . The pilot , ( TV : " Aliens of London " ) which Tosh nicknamed the " Space Pig " , ( TV : " Exit Wounds " ) was not dead , but in shock or hibernation . The creature ' s x - ray s were nothing like she had seen before , and Tosh assumed " that ' s what aliens looked like " . The creature , which was still alive , broke free from the morgue and injured Tosh . After soldiers shot down the shocked creature , the Ninth Doctor explained to Tosh that it was a ordinary Earth pig and " someone ' s taken [ the ] pig , opened up its brain , stuck bits on , then they ' ve strapped it in that ship and made it divebomb " . Tosh realised from this that the technology couldn ' t have been from Earth , and the aliens were faking aliens . She did not appear to realise that she met the Doctor . ( TV : " Aliens of London " ) In 2007 , Tosh had covered up a Cardiff hospital porter ' s murder by a Weevil she helped capture by planting a false alibi and changing the hospital ' s rota . ( TV : " Everything Changes " ) Tosh tracked the location of the meteorite containing a sex gas creature . When it escaped , she discovered the gas released ultra - powerful pheromone s . Tosh cornered the creature , which had possessed Carys Fletcher , at the Conway Clinic . There , Jack tricked it into escaping Carys into the portable cell , where it succumbed to the Earth ' s poisonous atmosphere . ( TV : " Day One " ) Tosh helped teammates Gwen , Jack and Owen track down the quantum transducer Bernie Harris was holding . ( TV : " Ghost Machine " ) Ianto Jones had helped awaken the partially cyber - converted Lisa Hallett from beneath the Torchwood Hub . The team escaped , but Ianto ran back to her . After Lisa had put her mind in the body of Annie , Ianto saw Tosh and the others shoot her . ( TV : " Cyberwoman " ) The Torchwood team travelled to the Welsh countryside to investigate a series of gruesome murders . The Torchwood SUV was stolen by a group of cannibals that harvested travellers once every ten years . The team followed the cannibals to their village . Right as his team were captured , Jack stepped in and incapacitated the cannibals . The cannibals were arrested by the police . ( TV : " Countrycide " ) Tosh had a lesbian affair with " Mary " , a female alien who tried to use their relationship to gain access to her technology , which Torchwood had previously confiscated . In order to gain Tosh ' s confidence , the alien allowed her the use of a pendant which granted her the temporary power of telepathy . Tosh used the device to save the lives of Carol and her child , about to be murdered in a domestic incident , but she became suspicious of the device when its use gave her insight as to how her teammates regarded her . Jack tricked Mary into being teleported into the Sun with her technology . Afterwards , Tosh decided to destroy the pendant , fearing what consequence such a device could have for human ity . ( TV : " Greeks Bearing Gifts " ) Gwen revived Suzie Costello with the resurrection gauntlet for questioning . Tosh was unable to look her former teammate in the eye . Instead of keeping her alive for a minute for a brief interrogation , Suzie kept the link between her and Gwen . After Jack ' s bullets were useless against Suzie , Tosh was ordered to destroy the gauntlet , which killed Suzie and saved Gwen . ( TV : " They Keep Killing Suzie " ) In 2008 , while investigating reports of loud music from the 1940s , the Rift brought Jack and Tosh into 1941 . She hid messages that preserved her half of the Rift equations that could bring her home . Owen used these to open up the Rift , bringing Jack and Tosh to the 21st century . ( TV : " Captain Jack Harkness " ) Owen ' s actions had caused cracks in space and time to spread from the Rift . While cleaning this mess up , Tosh saw an apparition of her mother , telling her to reopen the Rift and undo the damage . The team turned against Jack . Owen shot Jack and reopened the Rift to send everything that had come through back . The opening of the Rift forced out Abaddon , which Jack defeated . ( TV : " End of Days " ) Following Jack ' s departure , Toshiko was briefly promoted to team leader under Torchwood guidelines as their longest - standing member , but subsequently deferred command to Gwen when she was temporarily rendered mentally unfit to command after exposure to an alien artefact ( PROSE : " Kaleidoscope " ) . Tosh was part of a " wild goose chase " in the Himalayas when Jack went missing . ( TV : " The Sound of Drums " ) While chasing a Blowfish alien through Cardiff , Jack saved a family ' s life and quickly took over Torchwood again . Torchwood met an old lover of Jack ' s , Captain John Hart , who had came through the Rift searching for some canisters that had also come through . He told Torchwood that they contained radioactive bombs . Tosh tracked down where each of the canisters were . While searching for one of the canisters with Owen , John wounded them and stole the canister . Ianto recovered Tosh and Owen and Tosh found where Gwen had been poisoned so she could be treated . They caught up with John , but the contents of the canisters were actually components of a bomb that latched onto the DNA of the owner of the canisters ' murderer . Jack and Owen confused the bomb by injecting John with the DNA of the Torchwood team and safely disposed of it . John forcibly left 21st century Cardiff . ( TV : " Kiss Kiss Bang Bang " ) During one of Tommy Brockless ' yearly awakenings , the past and present time shift s began to occur , which the uniformed thought of as " ghost s " . To prevent a temporal catastrophe , Tosh and the team saw to it that Tommy returned to 1918 , after the couple had a short sexual relationship . ( TV : " To the Last Man " ) She fell in love with Adam Smith when he gave her memories that they were in love and when she was told this she still couldn ' t bring herself to take the retcon pill until she realised it was the right thing to do . ( TV : " Adam " ) While working on a time lock in the Hub , Tosh went to Russia . There , she worked with the KVI to investigate Zone 10 . She was given Object One by cosmonaut Anna Volokova , who was given it by the Committee . ( AUDIO : " Zone 10 " ) Tosh managed to reverse engineer the properties of the object in order to make it give good luck . Whilst using it , she stopped a war in Africa just by hearing about it , and went on a date with Owen , who kissed her . Believing that nobody should have that power , she sent it into another dimension and removed her memories of it using retcon . ( AUDIO : " The Torchwood Archive " ) Toshiko was personally responsible for shutting down the Pharm . By that time she had actually taken the initiative to ask Owen , with whom she had feelings , out on a date . She was extremely saddened when Owen was fatally shot in the chest by Aaron Copley . ( TV : " Reset " ) After Owen ' s return to life via the resurrection gauntlet early in 2009 , she still maintained hope for a relationship , to Owen ' s disgust given that his currently - deceased status prevented anything sexual from taking place . ( TV : " A Day in the Death " ) Later , however , he seemed less negative about the idea . ( TV : " Something Borrowed " ) Toshiko and the rest of the team minus Gwen were investigating an old factory that had detected Rift activity . She was caught up in an explosion of rubble and survived by the help of Gwen but had a broken arm . ( TV : " Fragments " ) Death . Tosh was shot by Gray while communicating via radio with Owen , talking him through his task of preventing a nuclear meltdown at a power station in Cardiff . She talked to Owen about how he would die from the meltdown and they discussed the date they had never gone on . Her wound was fatal and she died in Jack ' s arms after he arrived back at HQ with Gwen and Ianto . She told them how she had failed to save Owen . As the team deleted Tosh ' s profile on the computer system , an automated video message she had recorded played . In it , Tosh thanked Jack for saving her life , and proclaimed her love for Owen and the rest of the team . She reassured them that it was okay that she was gone . ( TV : " Exit Wounds " ) Legacy . Though dead , Tosh ' s presence was still felt by the others . When faced with certain death at the hands of the Dalek s , who were about to overrun the Hub , Gwen expressed her desire to " go out fighting , like Owen , like Tosh " ( TV : " The Stolen Earth " ) ; she and Ianto were saved by a time - lock defence system Tosh had been working on before her death . The Hub was sealed in a time bubble , preventing a Dalek from entering to finish them off . ( TV : " Journey ' s End " ) After the 456 incident , Jack revealed that he felt responsible for Tosh ' s death , along with those of all the other Torchwood operatives who died under his command . ( TV : " " ) The ghost of Ianto Jones ' father mentioned Toshiko among the loved ones his son could have seen again if he set Syriath free from the Cardiff Rift . ( AUDIO : " The House of the Dead " ) Whilst leaving Torchwood , Gwen mentioned how she loved Tosh , as well as Owen and Esther Drummond . ( AUDIO : " Herald of the Dawn " ) Personality . Tosh was a computer genius and arguably the most intelligent member of the Torchwood team . Despite her intelligence , she was insecure and not very confident in her abilities . Tosh was in love with Owen Harper but because of her insecurity , she found it hard to tell him how she felt . Tragically both Tosh and Owen were killed before they could get into a romantic relationship . ( TV : " Reset " , " Dead Man Walking " , " A Day in the Death " , " Exit Wounds " ) Tosh appeared to be bisexual , due to her relationship with a female shape shifting alien called Mary . ( TV : " Greeks Bearing Gifts " ) Behind the scenes . Torchwood website . The series 1 version of the Torchwood website had correspondence from Tosh in an unsent draft sent to her aunt discovered by Ianto . It was translated from Japanese into English by Ianto . It said that " for the last week " , Tosh was with a woman , referring to Mary , " going from a schoolgirl crush on Owen through to a fantastically fulfilling sex life with a complete stranger " . She called it " a week of firsts " , including : Tosh ' s first one night stand , lesbian kiss , lesbian " shag " , and the first time Tosh was late to work because of sex .