- Del Mar wakes up in his trailer, on a farm that's just been sold. He has to look for a new job, but he was dreaming about his lover Jack Twist, so he's in his happy place.
- Flashback to 1963, when Ennis and Jack Twist are both ranch hands. They were both poor and uneducated, so they opt for outdoorsy employment.
- They both sign up for ranch work and get assigned to sheep herding duties on Brokeback Mountain, Bo Peep apparently being off for the summer.
- They go drinking the night before they start work, and Jack tells Ennis about a lightning storm that wiped out a bunch of sheep. It probably sounds cooler than it actually was.
- They head up to the mountaintop. One of them sleeps out with the sheep to watch for predators, while the other one sleeps in the camp.
- Jack complains about staying out, so Ennis switches with him.
- Then, one night, it's too late for Ennis to return to the sheep, so they share the tent. One thing leads to another, and the two of them have sex.
- While they both insist that they're not gay, they continue the affair all summer.
- Unfortunately, their boss Joe Aguirre watches them through his binoculars. While he pays them at the end of the summer, he subtly calls them out for their tryst.
- The boys say their good-byes without knowing if they're going to see each other again. After they leave, Ennis feels bad enough to throw up.
- Ennis marries his girl Alma, gets a few odd jobs, and has a pair of little girls with her. They move into the town of Riverton and get an apartment above a laundry. Jack likes it because he can bolt from it easily.
- Jack twist writes out of the blue, saying he's going to be passing through Riverton and would like to see him.
- And when he shows up, well, you might say that it all comes flooding back. The two of them share a passionate kiss… right in front of Alma. Awkward.
- After making excuses about going out to a bar, they head to a motel and rekindle their affair up for real.
- Afterwards, they talk about their families and how much they dig each other. Jack wants them to get a little ranch together, but Ennis says that if anyone finds out about their forbidden love, they'll be killed. Also, it's not fair to his wife and kids.
- Ennis talks about two presumably gay men who lived near his folks. One of them turned up beaten to death with a tire iron one day. Ennis is not keen on following his example.
- So they head their separate ways again. Alma and Ennis grow apart, which isn't helped by the fact that he heads off on "fishing trips" with Jack a couple of times a year.
- They divorce, and she marries a grocer where she works and Ennis gets to play weekend dad.
- Ennis heads over the Alma's house one Thanksgiving. It goes well until she corners him in the kitchen and brings up his relationship with Jack.
- Jack, on the other hand, seems to be doing a little better. His father in-law-dies and his wife, Lureen, inherits a business selling farm equipment. Jack takes a job there and starts raking in the dough.
- In 1983, Jack and Ennis take another camping trip, which goes much the same way as all the other camping trips.
- On the third day of the trip, they come to words again. Jack is upset that they never had anything but these camping trips. Ennis, again, mentions the whole "they'll kill us if they find out" thing.
- Jack talks about going down to Mexico, where they can escape a bit of the prejudice that keeps them apart, but Ennis needs to work. He's been missing work and he has alimony to pay.
- Jack gets cranky. Mainly because Brokeback Mountain was the only place where they ever let their passions run free. Jack opines that he wishes he knew how to quit Ennis.
- Months later, Ennis sends Jack a postcard and gets a DECEASED notice back. And just like that, it's over.
- He calls the number he had and gets Lureen, who tells him that Jack was repairing a tire that blew up on him. Ennis suspects that Jack actually got beaten to death by homophobes.
- Lureen tells him that half of his ashes went back to Jack's folks in Lightning Flat, so he heads there in an effort to get the ashes and spread them back on Brokeback.
- It doesn't go very well. Jack's dad needs to prove that he's top dog and makes surly insinuations while Jack's mom tries to be nice. Ennis figures out that Jack got beaten to death thanks to dad's hints and suggestions.
- He goes up to visit Jack's old room and finds a pair of shirts hidden in a secret closet space. He takes the shirts with him as a token of their love, after dad refuses to part with Jack's ashes.
- He mourns Jack and dreams of him, too, knowing that he just has to stand the pain.