Brokeback Mountain has everything a good western needs: cows, cowboys, tough terrain, alliteration. But it has something else, too. Like many of the great westerns that came before it, it has a powerful theme.

The Searchers looks at what happens when racial hatred meets obsessive-compulsive disorder; High Noon took on Hollywood's reaction to the McCarthy "witch hunts" of the 1950s. But Brokeback Mountain, in its own small, very personal way, takes on what may be the most ironic aspect of the American myth: that two men, who are guaranteed by law the right of association, are refused the opportunity to associate with each other, at least in the manner they choose, by the very people who supposedly embody the spirit of American individualism -- cowboys. Tire-iron-wielding cowboys, you might say.

Like most adventures, however, Brokeback begins innocently enough. Ennis Del Mar (Heath Ledger) and Jack Twist (Jake Gyllenhaal) are just a couple of unemployed cowpokes when they arrive at the office of Joe Aguirre (Randy Quaid) looking for work. Ennis is between roundups, and Jack has pretty much given up rodeoing -- again.

They have little to say to one another. In fact, they pretty much just glare at each other across Aguirre's parking lot until he takes them in and gives them jobs tending a flock of sheep that's up in the high country for the summer. There Twist and Del Mar do all sorts of typical cowboy-turn-sheepherder sorts of things: smoke, eat beans, play the harmonica, make cryptic remarks.

No doubt they'd have remained a couple of guys instead of a couple if it hadn't been for a cold night, a bit too much to drink and Del Mar's decision to crash in Twist's tent instead of heading back to his high-mountain post.

And the rest, as they say, is histrionics.

But what makes Brokeback an exceptional love story is not that it's about two guys we don't normally think of as love bait for one another, but its careful mapping of the ripple effects of Del Mar and Twist's tryst.

With all of Wyoming to hide in, you'd think they could keep their feelings for each other a secret. But it isn't long before Aguirre catches them in the act, at least the act of foreplay, and not only do the sheep come down from the mountain early that year, but Twist loses the chance to ever go up with them again.

But more serious consequences await Del Mar and his soon-to-be bride, Alma (Michelle Williams). They marry, are fruitful and multiply, but there's the problem of Del Mar's unusual -- at least for 1963 -- style of lovemaking.

Twist, too, falls in love with a woman, a rodeo rider (Anne Hathaway), and they too are fruitful, though only half as fruitful as Del Mar and the aforementioned Alma.

But always at their back is Brokeback, and it's only a few years until Twist, who's hightailed it to Texas, returns to Wyoming for the first of a series of "fishing trips." And before you can say "trout stream," the feelings Twist and Del Mar share for one another rip open a gaping wound that runs from Wyoming to Texas and bleeds over into Juarez, affecting not only the two cowboys, but their wives, their children, their in-laws, Del Mar's post-divorce girlfriend (Valerie Planche), Twist's parents and the few friends they both have.

All this could have made for quite a mishmash, but in the hands of award-winning novelist/screenwriter Larry Lonesome Dove McMurtry, his co-writer/producer Diana Ossana (Streets of Laredo) and director Ang Lee (Crouching Tiger, Hidden Dragon), Brokeback comes across as a timeless piece of narrative fiction, heavy on character and quiet but quotable:

"You boys sure found a way to make the time pass up there," Aguirre tells Twist. "You guys wasn't gettin' paid to leave the dogs babysittin' the sheep while you stem the rose."

The mountains get their say as well. If you've never seen the Tetons -- or the Canadian Rockies, where much of the filming was done -- and if you don't expect you'll get to either before gas prices drop back down to $2 a gallon, go for it. Brokeback has camerawork any good western would die for.

And don't forget to give the soundtrack a listen. It starts simply, mostly some acoustic guitar picking. Then some Dobro and fiddle creep in. But before it's over, Lee and company are making ironic comments with Linda Ronstadt classics like "It's So Easy to Fall in Love."

Easy, yes. And dangerous. Brokeback will show you that, too.