 It was the first work in the "Doctor Who" universe to be written by future "Doctor Who" showrunner Chris Chibnall.The episode centres on Gwen Cooper (Eve Myles) working her first case with the alien hunters Torchwood in Cardiff, when she lets loose a purple alien gas that survives on the energy of orgasms.Over the course of the episode, the team hunt for Carys before the gas kills her.