Lord Peter Wimsey's elder brother the Duke of Denver is accused of murdering Dennis Cathcart. Cathcart was engaged to the Duke's sister Lady Mary, and was shot in the Duke's garden during the night. The Duke himself was discovered near the body, and it was his gun that was used in the murder. Wimsey and Bunter arrive from the continent and start to investigate the crime, hoping to save the Duke from the hangman's noose. (thetvdb.com)