

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.
Thanks to the clever briefing of the Lakin brothers a man charged with treason is found not guilty. Mrs Gale believes that Steed is implicated, and contacts the newspapers. Steed threatens her: either withdraw her allegations or pay the consequences. Soon Steed is on trial for Gale's murder.