Yvonne presided over Torchwood One at Canary Wharf, overseeing the Institute's major projects such as the Ghost Shift free energy project, the study of the Void sphere and the capture of The Doctor, who had been declared an enemy of Great Britain following his encounter with Queen Victoria and the Werewolf in 1879. While she was not hostile towards the Doctor and treated him as a guest at Torchwood, she fully intended to hold him captive indefinitely. Hartman was fiercely patriotic, and believed that Torchwood's work was vital to the survival of the "British Empire" and was certain that their work would in fact lead to the restoration of the United Kingdom to the status of world power. Only when the end was near did she attempt to stop the experiments, only to find that the Cybermen had already taken control over key members of her staff. The controlled staff proceeded to override her orders and allow the Cybermen to continue their invasion.
FateEditWhen the Daleks emerged from their Void ship and declared war against the Cybermen, Yvonne and several of her personnel were taken to a cyber-conversion suite for upgrading. As the terrified Hartman walked into the conversion chamber, she repeatedly reminded herself that she was doing her duty for Queen and Country, right up until the moment her head was sawed open and her brain was transplanted into a Cyberman body.
Though she was turned into a Cyberman, Yvonne's mind seemed to resist their programming and she retained her free will. As the Cybermen forces were losing the battle against the Daleks, a squad of Cybermen headed for the Torchwood Tower's breach room in order to escape back to their own universe. The cyberformed Yvonne blocked their path and blasted them with a lightning gun, a tear of black lubricant trickling from her eye as she repeated "I did my duty for Queen and Country". This is the last that is seen of Yvonne Hartman and it is not entirely clear what happened to her next. There are a few possibilities as to what may have happened to her:-
- Yvonne's mind may have continued fighting against her Cyber-programming for the whole time she was active, eventually leading to a fatal malfunction.
- Yvonne may have been killed by other Cybermen after destroying the four she encountered in the stairwell.
- Yvonne may have taken her own life as she could never become human again.
- She may have been sucked into the Void along with the Daleks and the Cybermen when the Doctor reversed the ghost shift.