The Strange Love of Martha Ivers (movie, 1946)

Three childhood friends, Martha, Walter and Sam, share a terrible secret. Over time, the ambitious Martha and the pusillanimous Walter have married. She is a cold businesswoman; he is the district attorney: a perfect combination to dominate the corrupt city of Iverstown at will. But the unexpected return of Sam, after years of absence, deeply disturbs the life of the odd couple.