Martha reappears in the second series (2008) of the "Doctor Who" spin-off, "Torchwood", which focuses on Captain Jack Harkness. First appearing in the episode "Reset" as part of a three-episode story arc, Martha has been temporarily drafted to the Torchwood organisation of alien-hunters by Jack, requiring a medical expert on alien life. Through exposition, it is revealed that Martha has become a "medical officer" for international paranormal investigations agency UNIT since qualifying as a Doctor of Medicine. Martha briefly joins the Cardiff-based Torchwood Three as its medical officer following the death of Owen Harper (Burn Gorman), but later leaves the organisation in the episode "A Day in the Death" once she is satisfied that Owen is fit to return to duty following his resurrection. Later in the fourth series of "Doctor Who" (2008), Martha returns for a three-episode arc beginning with the two-part story, "The Sontaran Stratagem" and "The Poison Sky", and ending with "The Doctor's Daughter", in which she meets The Doctor's new companion Donna Noble (Catherine Tate); in the first episode, a more assertive and engaged Martha summons The Doctor to Earth to help uncover a plot by the Sontarans. Martha returns again for the final two episodes of the series, "The Stolen Earth" and "Journey's End", where she has been promoted to a U.S. division of UNIT and is working on a top secret teleportation project based on Sontaran technology. She rallies alongside fellow companions Jack and Sarah Jane Smith (Elisabeth Sladen) in an effort to face the threat of Davros' (Julian Bleach) plot to destroy reality. In facing Davros, Martha threatens to set off nuclear warheads which will destroy the Earth in order to spare human suffering and curtail his plans, but is stopped by The Doctor. In the episode's dénouement, Martha leaves with Jack and former companion Mickey Smith (Noel Clarke), with Jack saying to her "I'm not sure about UNIT these days... maybe there's something else you could be doing."