À chacun son enfer (1977)

"A Chacun Son Enfer" (Everyone Has His Cross to Bear) is a horrible story, in which a mother discovers that after "the worst" there can still be something worse. Her daughter is kidnapped, but after paying the ransom, she finds her girl's dead body in a plastic bag. As the police investigate to unmask the killer, an awful doubt worms its way into the desperate mother's mind.