A train, six strangers, a murder... When appearances are deceptive and a killer is on the loose, every detail can hold the key.

One Friday evening brings six strangers together in a single sleeper car on a night train. Upon arrival the next day, a woman is found strangled. The remaining five—ostensibly witnesses, yet all strange and secretive—become suspects: a boxing fan, a young wife, a truck driver, an unemployed actress, and a young girl... who is nowhere to be found. The murderer, methodical and elusive, turns Paris into a theater of chaos. On Monday at police headquarters, everything changes: the person previously thought to be the victim is not the victim at all. Identities become blurred. Nothing is what it seems...