The Secret Adversary  (Hardcover, Agatha Christie)

Two young adventurers, recently demobilized after the Great War, form a partnership with the aim of "doing something daring." When they're hired to locate a missing woman tied to a state secret, they are swept into a dangerous conspiracy involving foreign spies, false identities, and a villain known only as "Mr. Brown." What begins as an innocent scheme soon becomes a race against time to prevent national disaster. With its clever banter, political backdrop, and fast-paced twists, the story introduces readers to an unforgettable duo-Tommy and Tuppence-whose charm and courage make them a delightfully different pair of sleuths. A mix of light-hearted adventure and sharp intrigue, this mystery combines youthful spirit with a plot of serious consequence.