Gray Gray was the younger brother of Jack Harkness . He lost his sanity following years of torture , becoming consumed by a hatred for his brother . Biography . Early life . Jack and Gray were boys in the Boeshane Peninsula when it was invaded by an unknown alien race described as " the most horrible creatures you could possibly imagine " , creatures that , according to Gray , lived to torture . Jack was told to run away and take Gray to safety . However , Jack let go of Gray ' s hand and lost him . He ran back but could not find him , and Gray was captured by the creatures . ( TV : " Adam " ) His captors branded him with a internee - identifying mark that remained permanently burned into the right side of his neck . Now a prisoner , Gray was torture d for years . Corpses piling up around him , Gray wished to die as well . Eventually , the other captives died and the creatures abandoned Gray , leaving him chained to a ruined city in the Bedlam Outlands with the " terrible things " he had learned at their hands . ( TV : " Exit Wounds " ) Revenge . Being found . John Hart , a Time Agent and Jack ' s former lover , discovered Gray chained in a ruined city in the Bedlam Outlands , surrounded by bodies , the creatures having long abandoned the place and Gray . Hart said he had no idea how long Gray had been alone before he was finally found . John soon realised Gray had changed . Gray never forgave his brother and his hatred consumed him . ( TV : " Exit Wounds " ) While visiting the year 2009 , Hart had given Jack the information that " they found Gray " . ( TV : " Kiss Kiss , Bang Bang " ) Revenge against Jack . Gray molecularly bonded a bomb to John ' s wrist and threatened to detonate it if John did not cooperate . ( TV : " Exit Wounds " ) Hart set a trap for the Torchwood 3 team and then let them see Gray in hologram form , giving the impression that John was the villain . ( TV : " Fragments " ) Having placed bombs around Cardiff , John detonated them to keep the rest of the Torchwood team occupied . Gray made John take Jack back to 27 AD Cardiff . Gray and Jack were reunited , only for Gray to stab Jack . Gray forced John to bury Jack alive , so he could endure a never ending cycle of suffocation and revival , as part of his revenge . Gray then set about destroying everything Jack cared for , travelling to 2009 and sending adversaries to the city through time and space . He also set Weevil s out into the streets of Cardiff , thanks to a high - pitched sound which came from a vortex manipulator . He detonated explosives across Cardiff , causing untold damage , killed the four highest ranking members of the Cardiff Police Force , caused a nuclear power plant to go critical and finally shot Toshiko Sato fatally while she was attempting to talk Owen through shutting down the reactor . The resulting overload caused the living - dead Owen to watch as his body collapsed . However , Jack was revealed to have been cryogenically preserved in 1901 after the Torchwood team of that era had discovered him . John Hart had betrayed Gray by burying with Jack a ring that emitted a tracking signal he hoped the Torchwood team could use to find Jack in the present . Jack told Gray that he ' d forgiven him , but Gray refused to listen . Jack tearfully chloroformed Gray and put him into storage until Jack thought that his brother could emotionally recover from the horrifying events , if at all . ( TV : " Exit Wounds " ) Personality . After being tortured for many years , Gray went insane and grew to hate Jack , blaming him for the agony he had been put through . Gray stabbed Jack when his older brother embraced him and took sadistic pleasure in the thought of having Jack endure a never ending cycle of deaths and resurrections . In addition to being sadistic and vengeful , Gray was ruthless and showed no remorse for committing murder , shooting Toshiko Sato and fatally wounding her . Gray was horrifically unforgiving , refusing to give Jack absolution even after his brother had forgiven him for all the horrendous crimes he had committed . He claimed that , after everything the aliens put him through , his hatred for Jack was the only strength he had left , clearly implying that without it , he would be nothing . In the end , Gray just wanted Jack to understand the pain he had gone through . ( TV : " Exit Wounds " )