When Marple was appointed as a board member of a merchant ship training ship, she felt very proud that the ship's mission was to transform young criminals. In all her efforts, Miss Maple intends to play an active role in this job, even wearing navy blue clothes to attend board meetings. When a trustee companion was poisoned before he made some disclosure, Miss Maple decided to use her position to stay on the ship for a period of time. This disrupted the fragile social network of the ship as it drove the roaring Captain Rhumstone out of his residence. When the two crew members were later discovered to have also been murdered, Miss Maple received help from her friends Jim Stringer and Detective Craddock to expose the culprit.