The Doctor's companion Rose first met Jack during the London Blitz in 1941, where he was posing as an American volunteer in the Royal Air Force. Rose and the Doctor had come to that time and place in pursuit of an alien cylinder that had crashed on Earth. Rose had accidentally hitched a ride on a barrage balloon and was about to fall to her death when Jack rescued her with his ship's tractor beam. Jack's ship — a stolen time ship of Chula design — was capable of concealing itself by turning invisible, and included in its systems nanogenes which could treat wounds.

While flirting with Rose, who was also attracted to him, Jack explained that he was a former Time Agent who left the organisation after discovering that two years of his memory had been removed, and going in search of them. Mistaking Rose and the Doctor for Time Agents as well, he tried to pass off the cylinder as an abandoned alien warship. In reality, the cylinder was a hollow and empty medical vessel — or so he believed. However, it was filled with billions of nanogenes, which began transforming everything they came into contact with (The Empty Child).

Jack assisted Rose and the Doctor in deactivating the nanogenes, but lost his own ship when he transported a German bomb on board to save the others from being killed by it. The TARDIS managed to rescue him before the bomb blew up his vessel, and he was taken on board as the newest member of the crew (The Doctor Dances).

It became apparent that Jack was (at least) bisexual, an orientation which the Doctor pointed out was more common in the 51st century, when mankind would deal with multiple alien species and sexuality would become more flexible. In Boom Town he flirted with the Doctor in front of Mickey, and the Doctor played along.

In Bad Wolf Jack became the first regular character in the programme's history to appear naked on screen (not counting the Third Doctor's shower scene in Spearhead from Space and Sergeant Benton at the end of The Time Monster), albeit discreetly shielded by strategically placed props. However, the BBC vetoed the production team's original intention of showing Jack's buttocks. In The Parting of the Ways Jack kissed both Rose and the Doctor good-bye, the latter being the first same-sex kiss in the programme's history.

Jack organised the defence of the Game Station against the Daleks in The Parting of the Ways to give the Doctor enough time to construct a Delta Wave projector. With the rest of his volunteer squad killed, Jack was the last to be exterminated, although Rose brought him back to life while she was suffused with the power of the time vortex. Neither the Doctor or Rose (whose memory was affected) seemed aware of his resurrection and left the Game Station in the TARDIS, leaving Jack behind.

However, in the Children in Need mini-episode, Rose suggests they go back for Jack, which means she either knows that Jack is alive or does not remember him being killed (she was not present when he died). The Doctor, in turn, replies that Jack is busy "rebuilding the Earth", indicating that he knows — or at least wants Rose to believe — that Jack had survived the final battle. How he came by this knowledge is unclear.

Executive Producer Russell T. Davies stated in Doctor Who Magazine that Jack was left behind because they wanted to explore the effects of the Doctor's regeneration (at the end of Parting) on Rose, since Jack would have taken the regeneration "in his stride."

His further adventures with the Doctor are yet to be revealed. Jack was originally reported as reappearing in the 2006 series, although not in the first block of episodes. According to Doctor Who Magazine #360, he will not be appearing at all in the 2006 series due to scheduling conflicts, although Barrowman has stated he will return for Series 3.

Torchwood

On 17 October 2005, The Independent reported that the BBC had commissioned Davies to produce a 13-part spin-off series titled Torchwood (an anagram of "Doctor Who"), set in contemporary Cardiff and investigating alien activities and crime. The series will feature John Barrowman playing Jack Harkness, and will premiere in Autumn 2006 on BBC Three. According to Barrowman, the series will not (at least initially) reveal how Jack comes to be in the 21st century. Check out our Torchwood section for more info on the series!