(Secret adversary): Investigating the case of a woman who has been missing for five years, Tommy and Tuppence Beresford uncover just enough information to solve the mystery and put their own lives in jeopardy.

Collected here are Secret Adversary and The Mysterious Affair at Styles the books that introduced the world to Tommy and Tuppence and to Hercule Poirot. These intricate novels revolutionized the mystery form and launched Agatha Christie's career.

"The Mysterious Affair at Styles" is a detective novel by Agatha Christie. It was written in the middle of World War I, in 1916, and first published by John Lane in the United States in October 1920 and in the United Kingdom by The Bodley Head on 21 January 1921. Styles was Christie's first published novel, introducing Hercule Poirot, Inspector (later, Chief Inspector) Japp, and Arthur Hastings. The story is told in first person by Hastings and features many of the elements that have become icons of the Golden Age of Detective Fiction, largely due to Christie's influence. It is set in a large, isolated country manor. There are a half-dozen suspects, most of whom are hiding facts about themselves. The book includes maps of the house, the murder scene, and a drawing of a fragment of a will, as well as a number of red herrings and surprise plot twists. "The Secret Adversary" is a work of detective fiction by Agatha Christie, first published in the United Kingdom by The Bodley Head in January 1922. The book introduces the characters of Tommy and Tuppence who feature in three other Christie books and one collection of short stories written throughout her writing career.

This anthology of rare stories of crime and suspense brings together 16 tales by masters of the Golden Age of Detective Fiction for the first time in book form, including a newly discovered Agatha Christie crime story that has not been seen since 1922.

Agatha Christie’s Tommy and Tuppence Beresford are Partners in Crime—or rather partners in crime solving—and must demonstrate their deductive skills in a wide range of confounding cases after agreeing to take over Blunt’s International Detective Agency. Tommy and Tuppence Beresford are restless for adventure, so when they are asked to take over Blunt's International Detective Agency, they leap at the chance. Their first case is a success—the triumphant recovery of a pink pearl. Other cases soon follow—a stabbing on Sunningdale golf course; cryptic messages in the personal columns of newspapers; and even a box of poisoned chocolates. But can they live up to their slogan of "Any case solved in 24 hours"?

IT was 2 p.m. on the afternoon of May 7, 1915. The Lusitania had been struck by two torpedoes in succession and was sinking rapidly, while the boats were being launched with all possible speed. The women and children were being lined up awaiting their turn. Some still clung desperately to husbands and fathers; others clutched their children closely to their breasts. One girl stood alone, slightly apart from the rest. She was quite young, not more than eighteen. She did not seem afraid, and her grave, steadfast eyes looked straight ahead. "I beg your pardon." A man's voice beside her made her start and turn. She had noticed the speaker more than once amongst the first-class passengers. There had been a hint of mystery about him which had appealed to her imagination. He spoke to no one. If anyone spoke to him he was quick to rebuff the overture. Also he had a nervous way of looking over his shoulder with a swift, suspicious glance. She noticed now that he was greatly agitated. There were beads of perspiration on his brow. He was evidently in a state of overmastering fear. And yet he did not strike her as the kind of man who would be afraid to meet death!

Hercule Poirot is about to tuck into a very traditional English supper with his old friend Bonnington when a lone diner sparks his interest. Like clockwork, the man has eaten at the restaurant on Thursdays and Tuesdays for the last ten years, but no one on the staff knows his name. When “Old Father Time,” as they have fondly nicknamed him, suddenly stops coming, Poirot believes that he might have picked up the one essential clue that could shed light on this mysterious man. Could what Old Father Time ordered as his final meal provide the key?