The Weekend Murders (1970)

An aristocratic English family gather for the reading of their father's will. The family are dismayed to find that everything has been left to Barbara, the deceased's favourite daughter. The butler is soon found stabbed to death and Sergeant Thorpe, the local bobby, telephones Scotland Yard for assistance. Inspector Grey arrives and he and Barbara narrowly escape being shot. Cousin Ted and his wife Pauline are both killed. Sergeant Thorpe recalls some photos which Ted asked to have developed...