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.
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.
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.