Jack begins as a time traveler and former con man from the 51st century. In contrast to the Doctor, Jack is a man of action, more willing to apply a hands-on solution to a problem. As a consequence of his death and resurrection in the 2005 series finale of Doctor Who, the character becomes immortal. On Earth, Jack becomes a member of Torchwood, a British organization dedicated to combating alien threats, becoming its leader over a century later. An ambiguous backstory is gradually revealed in the course of both series, adding another layer of complexity to the character.