For a while, Jack Harkness was a Time Agent in the 51st century, until the people he served wiped two years from his memory. In retaliation, he became a con man, seeking to profit from his former bosses. And then he met the Doctor, and Jack was transformed into a hero, traversing time and space... until he died, a victim of the dreaded Daleks. But Jack was revived and made immortal, only to find himself abandoned in the year 200,000. Jack eventually returned to present-day Earth and took control of the Cardiff branch of the Torchwood organisation, though his decades-long journey left him callous and detached, sometimes so focussed on the larger picture that he could forget about the small, fragile details which enrich humanity. Following his reunion with the Doctor and his growing attachment with his teammates at Torchwood, Jack is gradually finding his a place in a world in which he knows he will swell for all eternity.

John Barrowman has played Jack since Everything Changes in October 2006. He also portrayed the character in Doctor Who from The Empty Child to The Parting Of The Ways, from Utopia to Last Of The Time Lords, in The Stolen Earth / Journey's End, and in The End Of Time.

Unlike much of the rest of the Torchwood team, Gwen Cooper is neither a superhuman from the future nor a scientific wizard. What Gwen brings to Torchwood is heart -- a capacity for compassion, inspiration and understanding that her more aloof associates sometimes overlook or trivialise. But this also leaves Gwen vulnerable to the disturbing nature and torrid pace of her job, and with her husband Rhys' encouragement, she must work constantly to cling to the normal life which is so important to her.

Eve Myles has played Gwen since Everything Changes in October 2006. She also portrayed the character in the Doctor Who adventure The Stolen Earth / Journey's End.

For medical doctor Owen Harper, life in Torchwood was often little more than a game -- a chance to display his skills or engage in a spot of opportunism. He was cynical, moody, aggressive and self-centred, and did not suffer fools gladly, if at all. Nonetheless, Owen's sometimes brusque exterior masked a burgeoning passion for those things in which he truly believed -- a passion which could consume him on those rare occasions when it erupted to the surface, and a passion which seemed all the more keenly felt after he miraculously survived his first brush with death.

Burn Gorman played Owen from Everything Changes in October 2006 to Exit Wounds in April 2008.

Quiet to the point of being insular, Toshiko Sato was always more comfortable with her computers than with other people. Whereas Gwen made herself at home in Torchwood virtually as soon as she walked through its doors, Tosh found herself a perpetual outsider, never quite able to form a deeper relationship with her coworkers -- especially Owen, whom she secretly pined after. Yet Toshiko never stopped trying to break out of her shell, and more than made up for her awkwardness with her incredible skill and resourcefulness when it came to all things technological.

Naoko Mori played Tosh from Everything Changes in October 2006 to Exit Wounds in April 2008. She also portrayed the character in the Doctor Who episode Aliens Of London.

Whereas Toshiko was quiet by virtue of her meekness, Ianto Jones is quiet out of a sense of propriety. It is more important that he do his job attending to the unpleasant details of Torchwood's activities well, and justify his reputation for reliability, than that he be the centre of attention. But Ianto's mask of composure and efficiency hides a groundswell of emotion which erupts when those for whom he truly cares are threatened -- and so reserved is Ianto that this ardour can manifest itself in ways that are beyond his control, and border on the destructive.

Gareth David-Lloyd played Ianto from Everything Changes in October 2006 to Children Of Earth in July 2009. He also portrayed the character in Doctor Who in The Stolen Earth / Journey's End.

Even his wife, Gwen, is forced to describe Rhys Williams as “long-suffering”. When Gwen joined Torchwood, Rhys found the straightforward, stable course they were on abruptly thrown into chaos. Normally good-natured, trusting, jovial, and perhaps just a little thick, Rhys found himself becoming suspicion and untrustworthy, not just of the Torchwood team but of Gwen as well. Regardless, Rhys stuck by Gwen and the two found their relationship made even stronger through the crucible of Gwen's new experiences. Rhys now finds himself in the peculiar position of occasionally assisting Torchwood with its cases, even as he continues to yearn for that straightforward, stable life.

Kai Owen has played Rhys since Everything Changes in October 2006.

By the time she enjoyed a brief tenure with Torchwood, Martha Jones was no longer quite the same woman who had travelled in the TARDIS. A little older and more experienced -- and now a member of UNIT -- Martha demonstrated a degree of confidence and worldliness that she had not previously possessed. Ultimately, however, she was still the same plucky, determined woman who had explored time and space with the Doctor, and thus brought a new sense of fun and adventure to the subterranean halls of Torchwood HQ.

Freema Agyeman played Martha from Reset in February 2008 to A Day In The Death in February 2008. She also portrayed the character in Doctor Who from Smith And Jones to Last Of The Time Lords.

On November 30th, John Barrowman confirmed that he had been contracted for a fourth season of Torchwood, this one projected to run for a full thirteen episodes.