The Joad family has to move.
Tom returns home to find that his family has been kicked off of their land. The whole family has to pack up and leave Oklahoma.
Tom and the Joad family leave town.
The Joads buy a car and move west, like thousands of other families, in search of a new life, a new home, and new opportunity.
California is a myth.
On their journey westward, the Joads continue to hear news that things in California are dismal. However, they can't turn back. They have no life or home left in Oklahoma. They have no choice put to press on.
There's no work in California.
The Joads can't find any work in California. They are hungry, they are tired, they lose four members of the family.
We can work it out.
While Rose of Sharon's baby has died, she is able to use her breast milk to save a half-starved man. The Joads continue to reach out and to help anyone who needs help. We don't know what the future holds for the Joads, but we see their goodness and we know it exists in other families, too.