The Great War is over, and jobs are scarce. Childhood friends Tommy Beresford and Prudence "Tuppence" Cowley meet and agree to start their own business as The Young Adventurers. They are hired for a job that take them to many dangerous situations, including the wreck of the Lusitania, encounters with international spies, and an arch-criminal who's identity remains a secret to the very end.

The Secret Adversary introduces the popular characters of Tommy and Tuppence. Tommy, a young redheaded Englishman who fought in the Great War, was wounded twice. He is considered slow but steady and clear-headed in his thinking, and is at his best in a tight situation. Tuppence, a young woman with black bobbed hair, is one of several children of a conservative archdeacon. She served in the Voluntary Aid Detachment during the Great War. She is modern and stylish, quick and intuitive in her thinking, and acts rapidly on her ideas.

This case laminate collector's edition includes a Victorian inspired dust-jacket.