A debonair and diabolical villain turns a piece of scuba-diving equipment into an unusual instrument of murder in this clever chiller from the Hammer studios. Before the opening credits, we witness Peter van Eyck perpetrate what ought to be a perfect crime, rigging a room in his Italian villa into a death chamber for his wife. Her demise is ruled a suicide, but the killer's stepdaughter is the suspicious type; while she tries to unravel what really happened to her mother-and to her real father, who also died under dubious circumstances-a menacing relationship develops between sinister stepdad and troublesome teen. Formerly a cinematographer for David Lean and others, director Guy Green brings an inventive eye to the proceedings, which dive to a sardonic denouement.