The Secret Adversary by Agatha Christie

After the war, childhood friends Tommy Beresford and Tuppence Cowley decide to start a new life together—by advertising themselves as “Young Adventurers for Hire.” Their first job plunges them into a tangled plot of international intrigue, government secrets, and an elusive villain known only as “Mr. Brown.” Christie blends light-hearted charm with suspense, introducing a detective duo whose chemistry and wit would earn them a beloved place in her literary world. This is a fun, fast-paced thriller that highlights Christie’s skill beyond country house murders.