The Avengers S03 E04 The Nutshell

"Mrs Peel, We're Needed!"

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.