The Secret Adversary

While making a hasty exit due to a failed dine and dash attempt, Tuppence puts her foot in her mouth and referes to herself coincidentally as Jane Fish, they learn from an Intelligence agent that Jane Fish is actually a missing person who is highly sought after because she held a union treaty between several countries that could spark a new World War. It's up to Tuppence and her friend Tommy to find this woman, find out who is behind the crime before the evil man finds the document first. After splitting up and resolving sections of the crime the culprit turns out to be the Intelligence agent who gave them details to the crime in the first place. The duo save the day and by the end of the play get engaged.