Ruth Madoc, Jean Marsh, Colin Buchanan and Michael Byrne star in this thriller based on novelist Agatha Christie's work. Writer Mark Easterbrook has a vested interest in solving the murder of a priest. That's because Mark himself is under suspicion. But to save his reputation and put the real killer behind bars, he'll have to go through a mysterious list of names that's suddenly turned up and may hold the key to the murderer's identity.