Writers Jules (Oskar Werner) and Jim (Henri Serre) are close friends who fall in love with the same woman, the unpredictable Catherine (Jeanne Moreau), amid the turbulence of World War I Paris in one of director François Truffaut's best-loved films, adapted from the novel by Henri-Pierre Roché. What results is a decades-long love triangle that both tests and strengthens the bond between the two men.