Shots suddenly ring out in the bustling streets of Paris as gangsters attack a police van carrying notorious American criminal Eddy Roback to court. Eddy escapes, and Dufrense, a police inspector, receives word that he has been spotted at a department store. The police close the department store and begin evacuating the customers, but Eddy picks up a small child and flees the store undetected, leaving the child with a guard. He then goes to meet with his old associates, but arrives just as Dufrense and his men are raiding the hideout. That evening, Dufrense calls on Denise Vernon, Eddy's mistress, but she tells him she has a new lover, American newspaper correspondent Frank Clinton. He accompanies Denise to the restaurant where she is to meet Frank, and stations policemen at the entrance. Shortly after arriving, Denise tells Frank she must visit a sick friend, and sneaks out the service exit, then takes a cab to the gang's hideout and picks Eddy up. Eddy, who has a bullet in his arm from the morning's shootout, tells Denise he needs a large sum of money in order to escape over the Belgian border before daylight. They go to the apartment of their old acquaintance, Max Salva, who reluctantly takes Eddy in. After trying in vain to obtain the money Eddy needs, Denise rejoins Frank at the restaurant, and Dufrense comes in and subtly lets her know he is aware that Eddy has been in contact with her. Later, Frank tells Denise he knows she is seeing Eddy again and gives her most of the money she needs. Frank declares his love and warns that Eddy is just using her, but Denise protests that Eddy really needs her. Frank insists on driving her to meet Eddy, and after Denise has gone inside Max's apartment, Frank comes to the door with the rest of the money. Seeing Max as a possible informant, Dufrense has a policeman slip a note under his door, and after reading it, Eddy shoots Max and forces Frank to drive Denise and him over the border. After they leave, the badly injured Max crawls to the phone and calls the police, and when Dufrense arrives, Max tells him everything. Meanwhile, the fog grows heavy, and Eddy insists on taking the wheel. He crashes the car into a tree, but no one is injured, and they travel the last couple of miles on foot. After crossing the border, they go to a warehouse, where Eddy's gang is waiting, and Eddy instructs his men to put Frank on a train back to Paris. Frank urges Denise to come with him, but she tearfully refuses. She does not respond to Eddy's romantic overtures, however, causing him to fly into a rage and throw her out. Denise flees, but when she sees the police assembling in town, she runs back to warn Eddy. The hideout is soon surrounded, and a fierce shootout ensues between the police and Eddy's heavily armed men. Denise is struck by a bullet, and dies just moments after hearing the departing train's whistle. Eddy and his men are killed, and as Dufrense solemnly surveys the carnage, he pronounces the case closed.