The Mysterious Affair at Styles is a detective novel by British writer Agatha Christie. It was written in the middle of the First World War, 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.In her first published mystery, Agatha Christie introduces readers to the heroic detective, Hercule Poirot. This is a classic murder mystery set in the outskirts of Essex. The victim is the wealthy mistress of Styles Court. The list of suspects is long and includes her gold-digging new spouse and stepsons, her doctor, and her hired companion.