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.

According to Mary, Toshiko was 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. Her logout screen gave a date of birth as 19 September 1981.

Around 2003, though possibly in 2005, 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.

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.

While covering for teammate Owen Harper, who was suffering from a serious hangover, 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, which Tosh nicknamed the "Space Pig", was not dead, but in shock or hibernation. The creature's x-rays 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.

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.

Tosh tracked the location of the meteorite containing a sex gas creature. When it escaped, she discovered the gas released ultra-powerful pheromones. 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.

Tosh helped teammates Gwen, Jack and Owen track down the quantum transducer Bernie Harris was holding.

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.

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.

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 humanity.

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.

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.

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.

Tosh was part of a "wild goose chase" in the Himalayas when Jack went missing.

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.

During one of Tommy Brockless' yearly awakenings, the past and present time shifts began to occur, which the uniformed thought of as "ghosts". 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.

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.

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. 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. Later, however, he seemed less negative about the idea.

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.

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.

Though dead, Tosh's presence was still felt by the others. When faced with certain death at the hands of the Daleks, who were about to overrun the Hub, Gwen 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.

Biography from the TARDIS Data Core article, licensed under CC-BY-SA