When Of Mice and Men opens, we meet two guys just coming off a road trip to Salinas, California, where they've picked up some work: Lennie and George. They have an exactly-opposite-of-unique relationship. Exact opposite? In fact, it's one of the oldest relationships in the (any) book: George is the brains; Lennie is simple-minded but earnest. Sure, there's the added twist that Lennie is actually simple-minded, as in low IQ—but otherwise, it's your classic smart cynic/ lovable doofus pairing.
We also learn that these two guys dream about owning a farm together; that Lennie has a little problem with inappropriate (but totally innocent) touching; and that George has earmarked a place for Lennie to come if he ever finds himself in trouble.
And with that ominous discussion of "trouble," we're all set up to encounter it.
In come Curley and Curley's wife. Curley is immediately interested in Lennie because he's big and dumb, and thus an ideal candidate for Curley to abuse. Curley's wife also seems to take note of Lennie because he isn't as scornful as the others. Curley seems to be itching for a fight, and his wife is lonely. All told, this is bad news for Lennie.
The bad news: when Curley starts in on Lennie, Lennie fights back—and crushes his hand. The good news: Slim gets Curley to agree on a cover story to keep Lennie from being fired. The really bad news: we're pretty sure Curley has it in for Lennie. We don't like to use the phrase "perfect storm" too often, but this just might qualify: a ticked-off bully; a mentally challenged guy who doesn't know any better; and a woman who can't wait to get into trouble.
Lennie pets a puppy to death (not a euphemism) and then… pets Curley's wife to death. He knows something's wrong, but he doesn't know (like we do) just how bad it's going to be.
Curley is gunning (literally) for Lennie, and George realizes he's got to do something: he knows he can't let Curley shoot Lennie in the guts, but he can't handle the idea of having his friend locked up in a cage like an animal, either. What's going to happen?
This is really the only way it could play out: George shoots Lennie to save Lennie from a hellish life in an asylum or death at Curley's hands.
George continues on without Lennie or the dream farm.
George has done what seems to be the best option in the worst situation. We can be pretty sure a little piece of him has died with Lennie. Their friendship is over, and Lennie's death also brings the death of any faith that George had in the dream of a better life.