The TARDIS brings the Doctor, Ben and Polly to the planet Vulcan.  They see the murder of an Examiner from Earth and find a badge that allows unrestricted access to the colony there.  The Examiner had been called in to investigate rebel activities.

A Dalek spacecraft is found and the scientists there decide to revive the Dalkes that are on board.  The Daleks, upon awakening, claim that they are their rescuers' servants.  After gaining the trust of the humans, the Daleks create a reproduction plant.  The Doctor thwarts the Daleks by using power source of the colony to do so.