A... For Assassin

A wealthy diamond mine owner gets killed, and his relatives (who all hate each other) gather in the family villa for the reading of the will. They are told they must spend an entire month living together in the villa, during which time they will be eliminated down to only three heirs. An aging Scotland Yard detective is present to resolve the first crime that set this whole chain of events into motion. One by one, the relatives are eliminated until there is only one left. The title refers to a dagger with the letter "A" carved on it, which plays an important part in the mystery.