Married college professor Michael Lane falls in love with one of his students and hatches an elaborate scheme to dispose of his wife, Elizabeth. His murder plot goes as planned. However, he soon receives an anonymous note: "I know what you did, murderer!" Prof. Lane frantically tries to discover who knows his secret...

• Associated Television (ATV)
• Patrick O'Neal
• Angharad Rees
• Michael Kitchen
• Gerald Sim
• Gary Watson
• Patricia Donahue
• Terry Wright