An alien with the power to change memories infiltrates Torchwood, in this week's instalment of Doctor Who writer Russell T Davies's award-winning drama. It's up to the team to save themselves before it's too late.

With Captain Jack caught up in memories of his lost family, and Gwen struggling to remember Rhys, it takes Jack's love of Ianto to reveal the truth. But there's always a price to pay.

Captain Jack is played by John Barrowman, Gwen by Eve Myles, Rhys by Kai Owen and Ianto by Gareth David-Lloyd.