The United States' involvement in World War II has affected the trucking industry by increasing the need for truck transportation of goods while at the same time freezing the sale of new trucks. The top four trucking companies see this situation as a chance to force independent truckers out of business and establish a monopoly. At the instigation of Stephen S. Gray, the head of the Trans-State Trucking Company, the big four agree to hire gangster Tony Bonetti to carry out their plans. After Bonetti is installed as the head of Atlas Finance, the company that holds the loans on most of the independents' trucks, he begins to foreclose on all delinquent loans. Meanwhile, trucker Casey Dorgan stops for a cup of coffee and is inadvertently responsible for the firing of Eadie Watkins, a sassy waitress. A contrite Casey offers Eadie a lift and learns that her father is a friend and fellow trucker. Later, Bonetti addresses a trucker's meeting and advises them to sell their trucks now before they wear out and cannot be replaced. Casey argues against Bonetti and proposes instead that they form cooperative partnerships with produce suppliers. Bonetti's men then take Casey's truck, even though he owes no money on it, and destroy the produce suppliers' warehouses. One night, when Casey and his brother Jimmy, who is his partner, stop for coffee, Al Wilson, one of Bonetti's men, cuts the brakeline on their truck and Jimmy is killed in the ensuing accident. The district attorney investigates the wreck, but Casey, who wants to take his own revenge, refuses to tell them what he suspects. Because Casey was not killed, Bonetti refuses to pay Wilson. In an attempt to get rid of both Casey and Wilson, one of Bonetti's men tells Casey where Wilson is hiding. Not realizing that it is a trap, Casey hurries to Wilson's hideout, intending to learn who paid him to tamper with the truck. Bonetti's men are waiting outside, and as soon as Wilson agrees to talk, they burst inside and kill him. They then knock Casey unconscious and place the murder weapon in his hand. The police arrest Casey, who suggests that they pretend Wilson is still alive in order to lure Bonetti into trying again to kill him. The ruse works as planned, and with Bonetti's capture, the trucking war is over. Jimmy's widow Pearl has her baby, and after Casey, who is now married to Eadie, announces that he has joined the army, Eadie makes her own announcement that she is going to have a baby.