When Torchwood investigates a meteor impact, Gwen accidentally looses a gaseous lifeform contained inside. It possesses the body of a young woman named Carys Fletcher, who's been abandoned at a nightclub by her boyfriend. Under the extraterrestrial's influence, Carys lures one of the patrons into the nightclub washroom for sex... and watches as he disintegrates, while the entity feeds on the energies of his climax. Horrified, Carys realises that she must now kill men through intercourse or perish herself. With Jack, Tosh and Owen fixated on the alien being inside Carys, it's left to Gwen to try to save the woman's life.