Exile! The Time Lords have banished the newly regenerated Doctor to Earth. But the Doctor isn't the only alien to have arrived, as a swarm of meteorites have crashed into the sleepy English countryside, bringing with them a terrible new threat to mankind. As the Nestene plan takes shape, UNIT, the Doctor and his newly appointed scientific advisor, Liz Shaw, race against time to stop humanity being replaced by a terrifying plastic facsimile race.