Murder Ahoy
Tags: mystery, murder

Plot synopsis:
The action takes place mainly on board an old wooden-walled battleship, HMS Battledore, which has been purchased by a Trust for the rehabilitation of young criminals, and intended by the founder to put backbone into young jellyfish.
Shortly after joining the board of management of the Trust, Miss Marple (Margaret Rutherford) witnesses the sudden death of a fellow trustee, who has just returned from a surprise visit to the ship, much disturbed by something he has discovered there. He dies without being able to reveal his discovery. Miss Marple manages to obtain a small sample of his snuff, which is found to have been poisoned.
Resolving to learn what the murdered trustee had discovered, she visits the ship, while her dear friend and confidante, Mr. Jim Stringer (played by Margaret Rutherford's real-life husband Stringer Davis), investigates on shore. The Captain (Lionel Jeffries) takes an immediate dislike to her, and makes a sarcastic comment to his mate about her outdated formal naval attire, asking "Who does she think she is, Neptune's mother?" His distress intensifies when she announces her intention to remain on board several days, and to sleep in the Captain's own quarters, obliging him to move into his first mate's cabin.
That night, one of the officers is murdered – run through with a sword and then hanged from a mast. As the police investigation proceeds, the assistant matron is killed, apparently by an injection of poison. The investigation interferes with the ship's traditional celebration of Trafalgar Day. Somewhat unreasonably, the Captain blames Miss Marple for this. He begs Chief Inspector Craddock (Charles 'Bud' Tingwell) to find a way to get her off the ship, saying: "She's a jinx! She's a Jonah! She's blowing an ill wind!"
Miss Marple sets a trap: she announces to the crew that she knows that the poison was administered using a mousetrap as a booby-trap. She hints that she intends to reveal the murderer's identity shortly. She persuades Chief Inspector Craddock to allow the crew to go ashore for their Trafalgar Day celebration while she remains on board the deserted ship, with Chief Inspector Craddock and his assistant, Sgt. Bacon (Terence Edmond) secretly hiding in wait for the murderer to attempt to silence her. Sure enough, the first mate, Commander Breeze-Connington (William Mervyn), appears, and informs her that he has embezzled a large sum of money which he feels is owed to him because he was unjustly passed over for promotion, and that he committed the three preceding murders to avoid being exposed, and that he intends to kill her on the spot. Miss Marple calls out to Inspector Craddock to make the arrest, but he and Sgt. Bacon have accidentally been locked in their hiding place, and cannot help. Breeze-Connington draws his sword, intending to run Miss Marple through, but Miss Marple is herself an accomplished amateur fencer. She and Breeze-Connington engage in a ferocious sword-fight. Breeze-Connington succeeds in disarming her. He is about to administer the coup de grace, but Mr. Stringer, who, worried about her safety, had secretly rowed out to the ship in the dark, clubs him over the head from behind with a marlin spike.
The Captain faces a court martial for failing to prevent the embezzlement which occurred under his command. As he enters the state-room to hear the verdict, he sees his sword on the table with the hilt toward him, and mistakenly infers that he has been found guilty. Miss Marple corrects him; the board has found that he was not at fault. Although greatly relieved to have avoided disgrace, he announces that he must resign even so, because he has been having a long affair with the ship's Matron (Joan Benham), in violation of the golden rule of the trust that there should be "no hanky-panky between the sexes" on board ship, and they now intend to get married, which would disqualify him for his position as captain. He makes his farewell and turns to go, but Miss Marple stops him, saying, "I think I speak for my fellow trustees when I say that golden rule is hereby rescinded. You're a fine sea dog captain, but it seems to me the Battledore could do with a woman's hand at the helm." He and Matron embrace joyfully.
As Miss Marple steps into the dinghy to leave the ship, Matron and the Captain wave good-bye from the deck. The Captain turns to Matron and remarks, "You know, the moment I clapped eyes on her, I said to myself, 'What an old darling'!" Matron, remembering his actual first reaction, raises her eyebrows archly.