Perverse Relations (歪んだ関係, Yuganda Kankei), Kôji Wakamatsu, 1965

A doctor, gynecologist, discover the corpse of his wife. His nurse advises to him to declare her death a simple heart attack, to clear himself without the slightest doubt. He refuses and calls the police force there. The interrogation of the doctor, then other witnesses, slowly reveals the truth of her demise