A countess is strangled to death by her husband n later the husband is stabbed to death by an unseen killer. We have a daughter n her husband, an illegitimate son, a real estate agent n his girlfriend, a wierd entomologist n his even more wierdly dressed wife, all as suspects. Throw in some lousy hair teens n their girlfriends for nudity n body count. The film has ample body counts with solid effects, a nasty decapitation n a small shocking twist for that time. It has beautiful females, a bond girl, lil nudity but lousy sex scene, lousy hair teen boys, grey haired males n a very odd scene of a shotgun. As a master cinematographer, Bava succeeded in camera tricks to convince us that the film takes place near a forest but his tracking shots due to budget constraints were lousy.
In a shotgun with a double trigger, it is often possible to pull both triggers at once, firing both barrels simultaneously but it doubles the recoil, battering both shotgun and shooter n what if the shooter is a child?