“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.