Although Tom wishes to leave the family in order to save them from taking responsibility for his actions, the Joads nevertheless decide to leave Hooper Ranch for a location where Tom can be safe. They reach cotton fields up north, where Tom hides in the woods while the family stays in a boxcar. Although the family attempts to keep Tom's identity and location a secret, young Ruthie Winfield reveals it during a fight with another child. When Ma tells Tom about this, he decides to leave the family and go off alone, determined to fight for the cause for which Casy died. He vows to return to his family one day.
The rainy season arrives almost immediately after Tom leaves the family; massive flooding results from this weather. The Joads are caught in a dangerous situation: they cannot escape the flooding because Rose of Sharon suddenly goes into labor. While other families evacuate the camp near the rapidly rising creek, the Joads remain and attempt to stop the flood waters. Without the aid of others, the Joads are unsuccessful, and they must seek refuge on the top of their car. Rose of Sharon delivers a stillborn child that Uncle John sends in a box down the creek. The family eventually reaches higher ground and finds a barn for shelter. Inside the barn is a starving man and his young son. Steinbeck ends the novel with Rose of Sharon, barely recovered from the delivery, breastfeeding the dying man to nurse him back to health.