Still none the wiser as to the identity of Soviet agent 'N', Tommy and Tuppence must come up with their most ambitious and risky plan yet in order to protect the lives of British citizens.

Tommy and Tuppence turn their attention to their fellow occupants of Sans Souci to find N, the probable nuclear bomb thief.

The British Secret Service enlists Tommy and Tuppence's help again to find a Soviet agent and a kidnapped scientist.

Tommy's cover is blown, and the violent criminal gang give him a job to do. Tuppence comes to his aid as they try to prevent an assassination.

Tommy and Tuppence's search for the missing Jane Finn, Brown's identity and the recording gets more dangerous as they struggle to maintain their cover.

It's 1952, and Tommy and Tuppence Beresford, an ordinary married couple, are thrust into a web of international espionage after a chance encounter on a return train from Paris.