While attending a university near Geneva, a young American, Belle, stays at the home of Professor Stephane Blanchon and his frigid wife. Stephane becomes the principal suspect when Belle is found murdered in the Blanchon home. At the inquest it is revealed that although Belle dated often and was quite promiscuous, she had secretly been in love with Stephane. The news shocks Stephane into the realization that because of the brittle relationship with his wife, he has permitted his life to become aimless and listless, and as circumstantial evidence against him mounts, he shakes off his former passiveness and has a brief affair. Obsessed by the death of Belle and all he has missed in life, he kills the woman--ironically, he commits this murder at the very moment the police get a confession from Belle's killer.