The Director of Operations (Disco) of the Nutshell, a subterranean World War III bunker, tells Steed and Cathy that Big Ben, a file giving details of all their double agents, has been copied. Security cameras point to a young girl, but she is later found dead. Evidence implicates Steed, and Disco orders that he be apprehended.

When an agent is killed in the lift of Pinter's Department store, Steed and Emma get involved with King Kane, a tycoon who lives in a penthouse above the store. Why is Professor Popple, a missing atomic scientist, being held in the bargain basement?

When representatives of the two organizations head to a country church to investigate the sudden reappearance of a man long thought dead, Steed and Emma are called in to help. It isn't long, of course, before murder rears its ugly head.