The Market Basing Mystery

Hercule Poirot, Captain Hastings, and Inspector Japp are enjoying a weekend away in the little country town of Market Basing, when the local constable requests Japp's help. Walter Protheroe, the occupant of Leigh House, a nearby mansion, has been found dead in a locked room, apparently as a result of suicide. Japp, Poirot, and Hastings visit the scene. It is revealed that Protheroe was shot through the head and that his pistol is clasped in his right hand. Oddly, however, the bullet entered the head behind the left ear and, therefore, such a shot seems impossible. Poirot notes a handkerchief hidden in Protheroe's right sleeve, and also how fresh the air in the room smells despite the closed window and the multiple cigarette stubs in the ashtray and fireplace grate.

Protheroe's long-time housekeeper, Miss Clegg, informs Japp and Poirot that a couple, Mr and Mrs Parker, arrived unexpectedly three days ago and have been staying at Leigh House. Mr and Mrs Parker deny any involvement in the matter.

Two days later an inquest is held. A tramp, who often climbed over the wall of Leigh House to sleep in the shed, testifies that he heard Protheroe and Mr Parker argue about money at midnight on the night of the death, implying that the window had been open. Protheroe's true surname is revealed as Wendover. He had been involved with the treacherous sinking of a naval vessel some years earlier and Parker was blackmailing him over the incident. On the suspicion of killing Wendover and making it look like suicide, Parker is arrested.

Poirot talks with Miss Clegg. He surmises that Wendover did in fact kill himself, holding the gun in his left hand. Miss Clegg knew that Wendover was left-handed, a fact that Poirot deduced from the handkerchief in the right sleeve. She found his body on the morning after his argument with Mr Parker and, out of anger, decided to frame the latter as a murderer who staged the suicide, moving the gun to Wendover's right hand, closing the window, and locking the door.