The doctor takes Amy and  Roey to Apalapucia, not realising that the planet has been struck by a plague deadly to the Timelords.

When he and Rory are seperated from Any and stuck in seperate time streams, the Doctor must stay in the safety of the Tardis - both he and Amy relying on Rory to save her.

In a new timestream, Rory meets Old Amy, hardened by the time she's been waiting to be rescued.

When the Doctor finds a way to save Amy, at Old Amy's expense, she refuses to help - until she remembers her love for Rory and the connection they shared.