“Brokeback Mountain,” which began as an Annie Proulx story in these pages, comes fully alive as the chance for happiness dies. Its beauty wells from its sorrow, because the love between Ennis and Jack is more credible not in the making but in the thwarting. Duty calls; they go their separate ways, get married-one in Texas, one in Wyoming-and raise children. Ennis weds Alma, while Jack’s wife is a rodeo rider named Lureen, whose knowing wink, from the saddle, is the most brazen come-on in the film. After four years, the two men-as they now are-hook up again, and from then on they meet when they can. The most crushing moment comes as Alma glances from the doorway and catches her husband kissing his friend, in a rage of need that she has never seen before. In their frustration, the men are spreading ripples of pain to others, and the others are women and children. The female of the species suffers no less than the male, but she struggles to escape the suffering, whereas the male swelters inside his strange cocoon. That’s why, when Jack and Ennis part at the end of the first summer, Ennis slips into an alleyway, retches, and punches a wall-as if the only option, for the unrequited, were to waylay one’s own heart and beat it senseless.

In the end, this is Heath Ledger’s picture. There is no mistaking Jake Gyllenhaal’s finesse(look for the wonderful scene in which he can’t look-his jaw tightening as Ennis, still just a friend, strips to wash, just past the corner of his eye), but it is Ledger who bears the yoke or the movie’s sadness. His voice is a mumble and a rumble, not because he is dumb but because he hopes that, by swallowing his words, he can swallow his feelings, too. In his mixing of the rugged and the maladroit, he makes you realize that “Brokeback Mountain” is no more a cowboy film than “The Last Picture Show.” Each is an elegy for tamped-down lives, with an eye for vanishing brightness of which Jean Renoir would have approved, and you should get ready to crumple at “Brokeback Mountain”’s final shot: Ennis alone in a trailer, looking at a postcard of Brokeback Mountain and fingering the relics of his time there, with a field of green corn visible, yet somehow unreachable, through the window. This slow and stoic movie, hailed as a gay Western, feels neither gay nor especially Western: it is a study of love under siege. As Ennis says, “If you can’t fix it, Jack, you gotta stand it.”