Un temoin dans la ville 1959 Industrialist Pierre Verdier kills his mistress Jeanne Ancelin by throwing her off a train Her husband, Ancelin, decides to take revenge on his wifes murderer, who has been acquitted by justice He waits for him in his house and hangs him He leaves the place unseen, at least this is what he thinks But unfortunately for him, Lambert, a taxi driver has witnessed him Ancelin has no option but to get rid of him