The sole dissenting member of a jury that aims to convict a man of murdering an actress, beloved Agatha Christie character Miss Jane Marple (Margaret Rutherford) joins a theatrical company to investigate the crime on her own. As she gets closer to H. Driffold Cosgood (Ron Moody) and his fellow performers, yet another actor is found dead. Her digging uncovers evil deeds that date back several years, but Miss Marple finds herself in danger as she closes in on the killer.