What burns up as many calories as a game of squash, a five-mile run or a half-hour on a rowing machine? An evening at "Silverado," a movie guaranteed to get you up to 75 percent of your maximum heart rate. The western is back, and with writer/director Lawrence Kasdan at the reins, you're glad to see it. Yeeeeeeehaaaaaah!

"Silverado" unites four tough hombres, riding together but ready to go it alone, all handy with a gun, and all headed for the frontier town of Silverado. Emmett (Scott Glenn), a rangy, laconic pistolero, and his brother Jake (Kevin Costner), with a laugh as quick as his draw, are off to visit their sister; likewise, the rifle-toting Mal (Danny Glover), late of the Chicago slaughterhouses, rides to a reunion with his homesteading dad. The fourth, Paden (Kevin Kline) -- well, he's just looking for a little luck and the ultimate saloon.

When they finally arrive in Silverado, they find the place wrapped around the pinky of Sheriff Cobb (Brian Dennehy), a barrel-bellied nasty in the hire of a moneybagged crew called the McKendricks. Along the trail, there are jailbreaks, hoss stealin', fisticuffs and fancy shooting. The Magnificent Four come to the aid of a wagon train, including the lovely Hannah (Rosanna Arquette), face off against a comical British lawman (John Cleese) and outwit a gang of outlaws in "Box Canyon."

The movie has its slow going, particularly in the third quarter -- it takes too long working you up into a lather over the bad guys. But at either end, "Silverado" is a Great Rock Candy Mountain of a movie, in which every time you think you've hit the summit, Kasdan throws on another thrill. The action sequences are edited with beautiful precision (by Carol Littleton), and Kasdan orchestrates them with the pace of the old silent movie makers, following each sequence with a "topper." Although it might be impossible at this late date to play a western completely straight, Kasdan isn't involved in a spoof here -- the movie's leavened with humor, but it's not poking fun at the genre as much as giddily enraptured by it.

Kasdan (and his cowriter, his brother Mark) have cribbed a half-dozen plots from the past, so plot itself becomes incidental. Sometimes that gets "Silverado" in trouble -- the romantic triangle among Hannah, Paden and Emmett is so attenuated as to be ridiculous, and the oppressed homesteader riff works as a fifth wheel. But by the end, all the plots cancel each other out, in a way. "Silverado" becomes a kind of abstract reverie on the western, a mood piece, 100-proof western with all the good parts left in.

The Kasdans are skilled at writing attractive characters, parceling out themes and quirks that throw them in relief for the audience. Paden, for example, risked his life to save a wounded dog; he has a black hat he's fond of, just as Mal likes his long-barreled rifle, which he sometimes shoots from the hip, like a six-gun.

"Ensemble" is the most promiscuous adjective appended to "acting" these days, but "Silverado" is the real thing -- performances adding up to more than the sum of the parts. Bearded and scrunchy-faced, wandering the desert in a pair of long johns, Kline enters the movie as sort of a buffoon. But he lets the character grow into a sort of Mr. Steadfast -- even while bullets whiz and ping around him, he takes his sweet time aiming, but he never misses. Paden could veer off into sentimentality -- he's almost a parody of the Rainbow Coalition, savior of blacks, dwarves, children, poor people and wounded mutts -- but Kline invests him with a quiet intelligence that cuts the mawk the way lemon cuts oil.

Glover is sturdily serviceable as Mal; Glenn has the hard, lined features of a classic western hero. As his brother, Costner has a childlike charm -- the brows-knitted intensity of a kid getting the pegs in the right holes fragments in a mad laugh and a CinemaScope grin. With his perpetual look of surprise and gawky grace, he reminds you a little of Ray Bolger. And Dennehy is triumphant as the archvillain Cobb. There's something dangerous in Dennehy's small, ratlike grin, the way his sharp features are made punier still by his body, as bulky as the basso in a barbershop quartet. But he's lovably corrupt, too -- he has the knowledge of the world. In a '70s western, he, not Paden, would have been the hero.

Throughout, the casting is daringly contemporary (Kevin Kline in a western?), but for the most part it works, particularly in the cameos -- Linda Hunt adds piquance in a Belle Star turn, and Cleese is a howl as the Sheriff from the land of Shakespeare. Jeff Goldblum, on the other hand, as a sleazy derringer-toting gambler, is simply too contemporary in both looks and timing, and Arquette's brief appearance is a disaster, a whispery, nervous-making tour de floozy.

"Silverado" is an extremely self-conscious movie, referring explicitly to old movies and archetypes from the past. But it's not simply a movie about movies -- it's a movie about courage. And if courage, for "Silverado," means defending a saloon that smells the way a saloon should smell, so much the better.