The Secret Adversary is the second published detective fiction novel by British writer Agatha Christie. The book introduces the characters of Tommy and Tuppence. 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 leads them both to many dangerous situations, meeting allies as well, including an American millionaire in search of his cousin.