The Snorkel

From Hammer Films and director Guy Green, an atypical opening in which Peter Van Eyck, who will play a nasty Eurpoean step-dad, commits a perfect murder, in The Snorkel, 1958, also starring Betta St. John and Mandy Miller.

We know he's the killer but Peter Van Eyck (as sly stepfather Paul) is playing grief at his Italian villa, collected by Jean (Betta St. John), friend of stepdaughter Candy (Mandy Miller), whose mother was the victim, in Hammer Films' The Snorkel, 1958.