Imbued with the spirit of the left-wing political movement, Popular Front, which would have a major political victory that year, the film chronicles the story of M. Lange (René Lefèvre), a mild-mannered clerk at a publishing company who dreams of writing Western stories. He gets his chance when Batala (Jules Berry), the salacious head of the company, fakes his own death and the abandoned workers decide to form a cooperative. They have great success with Lange's stories about the cowboy, Arizona Jim — whose stories parallel the real-life experiences of the cooperative. At the same time, Lange and his neighbor, Valentine (Florelle), fall in love.
When Batala returns from the "dead", intending to reclaim the publishing company, Lange shoots and kills him (the "crime" of the title). Lange and Valentine flee to escape the country, stopping at an inn near the Belgian border. Here, Valentine tells Lange's story to a group of the inn's patrons, who had recognized Lange as the "murderer on the run" and threatened to turn him in to the police. After the story is through, the men sympathize with Lange and decide to allow him to escape across the border to freedom.
Source : Wikipedia