The novel begins with a detailed description of the lush rural area near the riverbed of the Salinas River a few miles south of Soledad, California. George Milton and Lennie Small, two men dressed in denim, are walking along a path on the riverbed. George, the leader, is small and quick. Lennie, huge and awkward, follows behind.
George and Lennie's denim clothing show that they're poor ranch hands. Their single-file walking pattern reveals the dynamics of their relationship: George is the leader even though Lennie is larger.
The men stop. Lennie drinks huge gulps from a pool of standing water next to the river. George warns him not to drink too much or else he'll get sick again.
Lennie's lack of common sense is the first indication of his mental disability.
When George complains about the bus driver who dropped them off too far from the ranch, Lennie asks where they're going. George reminds Lennie about their plans, but stops when he notices a dead mouse in Lennie's pocket. Lennie picked it up because he likes to pet its soft fur, but accidentally killed it.
George clearly acts as a kind of parent to Lennie. Petting the mouse shows Lennie's innocence and the unintended consequences of his strength.
George throws the mouse away, and tells Lennie they're going to a ranch like the one they just left in Weed. George also tells Lennie not to say anything when they meet the boss at the new ranch.
George constantly worries that Lennie's disability will jeopardize their welfare and their future.
Lennie remembers that they were "run out" of Weed, but George says they ran away before they could be run out. George then says that his life would be so much easier and more free if Lennie wasn't always following him.
Given that Lennie keeps getting them fired, George is right: his life would be easier without Lennie. So why does he stay with Lennie?
George decides they should spend the night where they are. Lennie goes off to find firewood. While he's gone George thinks of him as a "poor bastard." When Lennie returns without wood, George suspects he's found the dead mouse again. George takes it, making Lennie cry. Lennie mentions how his Aunt Clara used to give him mice. George reminds Lennie that he always accidentally killed them.
Behind George's scolding and frustration are pity and love. Lennie's history with mice shows that he often destroys the things he loves, foreshadowing his fate. Aunt Clara's death shows the lack of family and community in the ranch workers' lives.
The men have a dinner of canned beans. When Lennie complains about the lack of ketchup, George again says how much easier his life would be without Lennie. He brings up the event that got them run out of Weed: Lennie touched a woman's dress and refused to let go. She accused him of rape. Lennie liked the dress because it felt soft as a mouse's fur.
George's bachelor fantasy shows how his feelings of responsibility for Lennie interrupted the plans he had as a youth. Lennie's obsession with soft things extends to women.
Lennie offers to leave George alone and go live in a cave. Lennie imagines that he could keep mice in his cave if he wanted to, without George's supervision.
Lennie understands he's a burden. He also has his own desire for freedom.
George says he wants Lennie to stay with him. He comments that ranch workers are always lonely, but he and Lennie are different. They have each other.
Deep feelings of friendship and loyalty keep George with Lennie.
At Lennie's urging, George describes their future. They'll save money until they can buy their own farm. George describes the farm right down to its rabbit hutches. Lennie can't contain his excitement about tending rabbits and living off the "fatta the lan."
The farm is George and Lennie's American Dream. This dream of a future together is the fullest expression of their friendship.
As they go to sleep, George asks Lennie to take a close look at their surroundings. He tells Lennie that if he gets into any trouble at the ranch he should back to this spot and hide in the bushes.
Yet even at this hopeful moment, George senses that Lennie's mental disability will dash their hopes.