Oklahoma farmers dispossessed during the Depression fight for better lives in California.

Tom Joad returns from prison, where he was serving time for manslaughter, to his family's Oklahoma farm and finds the house abandoned. Muley, his half-crazed neighbor, tells Tom about the recent dispossession of the sharecroppers, who have been driven out by drought and the greedy land companies. Tom finally locates his family as they are about to pack their belongings on a dilapidated truck and head West, lured by promises of work and high wages in California. Joined by their friend Casy, a former "fire and brimstone" preacher, the Joads begin their long trek west on Route 66. Soon after, Grandpa dies and is buried alongside the road. Their hopes for a bright future are dimmed when a man at a roadside camp warns of no work in California, but the family continues on. As the Joads cross the great California desert, Grandma dies, and the remainder of the family emerges from the desert to find no jobs and hoards of starving migrants. Poverty and desperation begin to break apart the family as the husband of pregnant daughter Rosasharn leaves her. Despite rumors of labor violence, the family nonetheless hits the road once again. Hounded by the law and the local citizenry, the Joads find work as strikebreakers. Casy warns Tom that strikebreaking will only drive down wages, and when a deputy murders Casy for his labor organizing, Tom fights back and kills the deputy. With Tom now hunted as a murderer, the family steals away under cover of night and finds temporary refuge in a government agricultural camp. When the police track Tom down at the camp, however, he is forced to bid farewell to his family, knowing he may never see them again. As the family leaves the haven of the camp for promise of work in Fresno, Ma Joad voices the faith to carry on.