Right from the outset, we know what has happened to "Mrs. Dexter". We see the clever method by which she is gassed to death - but there is something a little bit ingenious about the fashion in which her husband "Paul" (Peter van Eyck) executes, quite literally, his wife. The police arrive, and finding the room locked and taped up assume quite naturally that she has taken her own life. Her daughter "Candy" (Mandy Miller) isn't buying it. For years she has been claiming that she saw him (her stepfather) kill her real father whilst boating, and now she is determined to get to the bottom of it…