Tommy and Tuppence have a chance encounter on a train with an agitated young woman who suddenly disappears and never returns to her seat.

Tommy and Tuppence go undercover; he as a member of Brown's gang and she as a maid to a potential suspect.

The Beresfords' search for Jane Finn comes to a close as they finally uncover the identity of Mr. Brown.

Tommy is sent on a secret mission to discover the identity of Soviet spy staying at a seaside guest-house; Tuppence refuses to be left behind.

There is a murder at the local Veterans Ball, as Tommy and Tuppence continue their search for the Soviet spy.

Tommy and Tuppence have to come up with their most ambitious and risky plan yet in order to protect the lives of British citizens.