During an annual board of trustees meeting, one of the trustees dies. Miss Marple thinks he’s been poisoned after finding a chemical on him. She sets off to investigate at the ship where he had just come from. The fourth and final film from the Miss Marple series starring Margaret Rutherford as the quirky amateur detective.
Miss Marple believes she's seen a murder in a passing-by train, yet when the police find no evidence she decides to investigate it on her own.
Miss Marple and Mr. Stringer are witnesses to the death by heart attack of elderly, rich Mr. Enderby. Yet they have their doubts about what happened. The police don't believe them, thus leading Miss Marple to yet again investigate by herself.
A murderer is brought to court and only Miss Marple is unconvinced of his innocence. Once again she begins her own investigation.