Georges Manda (Serge Reggiani), an honest woodworker, falls in love with Marie (Simone Signoret), the moll of minor crook Roland (William Sabatier). Gangster boss Felix Leca (Claude Dauphin) orders Georges and Roland to fight a duel to the death over the girl. Felix then pins the blame for Roland's death on Georges' boyhood chum, Raymond (Raymond Bussieres), knowing that the woodworker will nobly accept the blame; this will leave Marie alone, which is what lustful Felix has wanted all along. When Georges learns he's been set up as a dupe, he plots his revenge. Based on the true-life Leca-Manda scandal, 'Casque D'Or' brilliantly mixes violence with tenderness to capture the brutality of the French underworld and the tragedy of doomed love.