All of time and space hangs in the balance, for this is the day the Doctor dies.
The Doctor (Matt Smith) attempts to escape his apparent death at the hands of the Silence. River Song (Alex Kingston), whom the Silence had programmed to kill the Doctor, refuses, and they end up in an alternate timeline where all of time is running simultaneously and beginning to collapse. The Doctor tries to restore the universe with the help of River and the alternate universe versions of his companions Amy Pond (Karen Gillan) and Rory Williams (Arthur Darvill). It is revealed that he had already planned escape by posing as himself using the shape-shifting Teselecta.