The blueprints of an aeroplane built from an ultra-secret metal are stolen from national security. French secret service agent Walder believes that the documents are now in Switzerland, in the hands of a man named Lindbaum. The latter agrees to hand over the blueprints in return for a large sum of money. Another agent, Francis Coplan, is sent to Switzerland to handle the deal, but Lindbaum only has half of the documents because he was double-crossed by Kalpannen, an international crook. With the help of Heidi, a Swiss correspondent, Coplan sets out to identify the members of Kalpannen’s gang, only to find that they have all been murdered…

Yves Tréguier, a young orphan, escapes from a reform school in Brittany to join "Dédé la Glace" in Paris, an old-timer with whom he has a sincere friendship. The love of Zette, a young girl he has met, and the benevolent friendship of Father Blain, the bistro owner, give him the desire for regular work. "Jo le Grec", a pimp jealous of Dédé's friendship with Yves, seduces Wanda, a prostitute he loves, and shoots Dédé dead. Blain prevents him from doing the same to Yves, and shoots him in turn. Yves can live an honest life with Zette and the baby she's expecting.