The Secret Adversary

It is the first novel to feature the characters of Tommy and Tuppence who would go on to appear in several more of Christies works. The story is set in post-World War I London where the young and adventurous Tommy Beresford and Tuppence Cowley have recently been demobilized from the army. They are struggling to find work and decide to set themselves up as young adventurers offering their services as investigators. They are hired by a mysterious figure known only as Mr. Whittington to find a woman named Jane Finn who disappeared after the sinking of the Lusitania during the war.