In the second episode of the first series of the British science fiction show *Torchwood*, Gwen Cooper’s first official case involves a gaseous alien entity that escapes a meteor and sustains itself by absorbing energy during human orgasms. What is the title of this episode?

"Day One" is indeed the title of the second episode in the first series of the British science fiction show *Torchwood*. This episode, which originally had the working title "New Girl," marks Gwen Cooper's true initiation into the extraterrestrial-hunting team. It was written by Chris Chibnall, who would later become a showrunner for *Doctor Who (Review)*, and first aired on October 22, 2006, immediately following the series pilot, "Everything Changes."

The plot centers around Gwen accidentally releasing a purple gaseous alien entity from a meteor that crashed near Cardiff. This alien then possesses a young woman named Carys and sustains itself by absorbing energy from human orgasms, leaving its victims as piles of dust. Torchwood's investigation into the bizarre deaths leads them to discover Carys and the alien's unusual method of feeding. The episode highlights Gwen's developing role within the team, as she displays a strong sense of humanity and concern for the alien's host, contrasting with some of the more hardened members of Torchwood.

"Day One" was notable for being one of the first productions in the *Doctor Who* universe to explicitly center a conflict around sex, taking advantage of *Torchwood*'s post-watershed broadcast slot. This choice aimed to establish the show's more adult tone compared to its parent series. The episode also features some humorous moments, such as Gwen's accidental release of the alien while attempting to assert herself against Owen, and the team's discussions about Captain Jack Harkness's mysterious background.