The Paris demimonde of 1900 is the setting for Casque d'Or. 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, as prescribed by the code of the apache.
Felix then pins the blame for Roland's death on Georges' boyhood chum, Raymond (Raymond Bussières), knowing that the woodworker will nobly accept the blame; this will leave Marie alone, which is what the lustful Felix has wanted all along. When Georges learns he's been set up as a dupe, he escapes from the police and kills Felix.
Casque D'Or was based on the true-life Leca-Manda scandal, wherein an otherwise decent man was guillotined for shooting down a gangster boss in broad daylight. Since the scandal was common knowledge in France, the downbeat ending of this film was hardly unexpected but still extremely moving.
Completed in 1951, Casque D'Or was a failure on its first release but then built up an excellent word-of-mouth reputation abroad. The film was released in the U.S. in 1956 as Golden Marie.