A bank teller finds a piece of plastic in a fence one day and notices a strange man in a scarf trying to get the teller's attention.
At the bank the man, introducing himself as the Doctor, discusses the plastic with the teller, who thinks he is crazy. The teller is attacked by a vending machine on the way home and is rescued by the Doctor, who explains that the plastic is sentient. The Doctor retrieves the plastic and promises to take it home.
Later, at home, the teller can hear strange scratching noises.