Doctor Who: The Space Museum/The Chase
The Space Museum
The TARDIS jumps a time track and the travellers arrive on the planet Xeros. There they discover their own future selves displayed as exhibits in a museum established as a monument to the Galactic conquests of the warlike Morok invaders who now rule the planet. When time shifts back to normal, they realise that they must do everything they can to try to avert this potential future.
The travellers are forced to flee in the TARDIS when they learn from the Time/Space Visualiser taken from the Moroks' museum that a group of Daleks equipped with their own time machine are on their trail with orders to exterminate them.