After their return from a parallel world, the Doctor, Amy, Natalie and K9 join forces with Jack Harkness and Gwen Cooper to solve the mystery of the Miracle that erased death. Faced with such an unconventional threat, the Doctor must explore how far he will go in the name of history when so many lives are at stake in a manner he can't easily condemn or overcome.
When Rory and Amy meet Rhys, Gwen, and Gwen’s boss Jack, they find that they have more in common than they think (such as a certain time-traveling alien).