In a world inhabited by killers and cheats, architect Walter Saccard is unhappily married to Clara. His idle interest in the spousal murder case of bookseller Melchior Kimmel becomes something more intense when the accused is acquitted, and Walter, who believes him guilty, strikes up his acquaintance. When Clara is found dead, Kimmel in turn believes Walter responsible, while a detective suspects the two deaths to be connected in this twisting, suspense-drenched masterpiece of mainstream French cinema made at the height of the Nouvelle Vague.