"Can't," he says. "I'm still in contact with UNIT in another timeline. Can't walk into myself, might cause a catastrophic collision. That, and my younger selves are always asking me for money."

He slips his key into the lock and pushes on the door. It doesn't budge. Another push, and then it finally creaks open. The room itself is cramped, with hideous orange carpeting and bright pink walls. The television, the coffee maker, and everything with wires in the room apart from a single lamp has been stripped and cannibalized for the Doctor's latest gadgets.

"Home sweet home," he says. "For now."