Explain what happens between Lennie and Curley's wife?

In Chapter Five, Curley's wife enters the barn in a dress decorated with red ostrich feathers. Lennie, who has been warned to have nothing to do with her, tries to resist being drawn into conversation, but she prevails, telling him that the other men are too busy with their horseshoe tournament to care whether he talks to her or not. She sees the dead puppy and consoles him, saying that no one will care about the loss of a mere mutt.

She is clearly starved for conversation and launches into a reprise of her discontented story of what might have been. She insists that she could have been an actress. Lennie fails to understand her at all, however, as he continues to return to the dilemma of the dead puppy and his anxiety over being denied the right to tend the rabbits. Curley's wife angrily asks him why he is so obsessed with rabbits, and Lennie thoughtfully replies that he likes to pet nice things.

Curley's wife observes that Lennie is "[j]us' like a big baby" (99) and invites him to stroke her soft hair. Lennie begins to feel her hair and likes it very much indeed, which leads him to pet it too hard. Curley's wife begins to struggle, which sends Lennie into a panic. He grabs a hold of her hair and muffles her screams. When she continues to struggle, Lennie grows angry. He shakes her violently, telling her to keep quiet so that George doesn't hear her. Before he knows it, he has broken her neck. She lies dead on the hay. Lennie observes that he has "done a bad thing" (100) and covers her body with hay. He then disappears from the barn with the dead puppy in hand.