Brothers and Sisters (1980)

Synopsis
This murder mystery has an unusual twist: the puzzle over who did it takes a back seat to the effects of the investigation itself. A large, partly-communal household is thrown into disarray when a part-time prostitute is murdered and members of the household come under suspicion. James Barratt (Robert East) is an arrogant aristocratic type who initially seems to be the killer. That possibility becomes less likely when he evolves into a decidedly honest person. His younger brother David (Sam Dale) is also a suspect, especially when his likeable nature turns out to be flawed. Their sister Sarah (Elizabeth Bennett) also loses some of her reasonable exterior when push comes to shove. Other characters move in and out of an investigation that threatens to reveal more about psyches and relationships than about the unknown killer. ~ Eleanor Mannikka, All Movie Guide