After the Toymaker zapped the 14th Doctor with a galvanic beam, it causes him to "bi-generate" into the 15th Doctor while the previous incarnation stays. The two Doctors defeat the Toymaker in a game of catch and banish him from existence as he threatens his legions' arrival. Before departing in his TARDIS, the new Doctor creates a new one for his predecessor, who decides to settle down on Earth with Donna and her family.