A thrilling espionage and mystery novel by Agatha Christie that introduces the adventurous detective duo Tommy Beresford and Tuppence Beresford. Set shortly after World War I, the story follows the two young friends as they launch a business venture called "The Young Adventurers, Ltd." and soon become involved in a dangerous search for a missing woman and a secret document of national importance.

Their investigation leads them into a world of spies, conspiracies, disguises, and international intrigue, where they must outwit a mysterious criminal mastermind known only as "Mr. Brown."