She who was no more - Boileau-Narcejac

Every Saturday evening, travelling salesman Ferdinand Ravinel returns to his wife, Mireille, who waits patiently for him at home. But Ferdinand has another lover, Lucienne, an ambitious doctor, and together the adulterers have devised a murderous plan.

Drugging Mireille, the pair drown her in a bathtub, but in the morning, before the "accidental" death can be discovered, the corpse is gone--so begins the unraveling of Ferdinand's plot, and his sanity...

This classic of French noir fiction was adapted for the screen by Henri-Georges Clouzot as Les Diaboliques (The Devils), starring Simone Signoret and Vra Clouzot, the film which in turn inspired Alfred Hitchcock's Psycho. A second movie version, Diabolique, followed in 1996, starring Sharon Stone.