The Mystery of the Locked Room

Cases from the practice of the greatest detective of all time, which his friend and assistant Dr. Watson only mentioned in his stories. The most unusual crimes and the most mysterious investigations that Sir Arthur Conan Doyle himself intended, but did not have time, to recount, and which were completed by his son Adrian Conan Doyle and the celebrated master of classic detective fiction, John Dickson Carr!
The room was locked with a key. Inside were Colonel Warburton and his wife. First the colonel shot his wife, and then shot himself. What drove him to this act? Had he perhaps gone mad?