Rat

A man confronts his past during an experiment that attempts to find a solution to the problems of a post-apocalyptic world caused by a world war.

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.