The TARDIS arrives on Earth with a newly regenerated Doctor on board.  He is found and taken to a hospital.  The Brigadier and new recruit Liz Shaw go there to see if the reports of the Doctor's reappearance is correct.  The Brigadier doesn't recognize him.  Several meteorites came down with the TARDIS which turn out to be globes that contain the Nestene consciousness.  A human, Channing, has infiltrated a plastics factory and is using energy from the globes to animate Autons.  Autons are plastic figures that can be inhabited by the Nestene and used to move around.  Realistic replicas of government and military poeple are being made also with the intent of conquering the world.

The Doctor recovers from his regeneration and help UNIT to defeat the Nestene consciousness.  Channing is found to be a sophisticated Auton.  The Doctor agrees to work for UNIT as its scientific advisor in exchange for the use of a lab to help him attempt repairs on this TARDIS.