Tommy and Tuppence have a chance encounter on a Paris train with an agitated young woman, named Jane Finn, who suddenly disappears and never returns to her seat. Intrigued by the case, the couple discovers Ms. Finn was carrying a secret recording that would potentially reveal the identity of a legendary Soviet assassin, known only as Mr. Brown.Tommy and Tuppence have a chance encounter on a Paris train with an agitated young woman, named Jane Finn, who suddenly disappears and never returns to her seat. Intrigued by the case, the couple discovers Ms. Finn was carrying a secret recording that would potentially reveal the identity of a legendary Soviet assassin, known only as Mr. Brown.