Robot A series of burglaries perpretrated by something more than human leads the newly regenerated Doctor and UNIT to the doors of the progressive Think Tank organisation which intends to hold the world to ransom. The Ark In Space On Space Station Nerva in the distant future, the remnants of humanity are held in cryogenic suspension. But the station has been invaded by parasitic Wiirn who intend to feed on the humans and conquer the Earth. The Sontaran Experiment Believing the Earth of the far future to be uninhabited, the Doctor, Sarah and Harry encounter Field Major Styre - the advance guard of a Sontaran invasion.