The third episode of this supersonic comic strip drops all pretense to character and motivation. When we first met Riggs in the title role of " Lethal Weapon" (1987), he was a suicidal wild man whose death wish was the result of a tour in Vietnam and the loss of his wife. In “Lethal Weapon 2,” the immortal toilet-seat-bomb scene was a clever spin on the theme of male bonding. In LW3, after five years with Murtaugh and his clan, Riggs’s mad-cop ways have become self-amused style. When he offhandedly tries to defuse a bomb and blows up an office building, or when he pulls his gun on a terrified jaywalker, he’s just having fun scaring the pants off his cautious partner. LW3 is violence as pure farce; Murtaugh and Riggs have become the Abbott and Costello of buddy-cop flicks.

This may well be the recipe for a third LW box-office smash. Or will the recent riots make moviegoers uneasy about L.A. cops engaging even in slapstick carnage? Director Richard Donner choreographs violence like Busby Berkeley with Uzis instead of floozies. And writers Jeffrey Boam and Robert Mark Kamen have stumbled at some key points. The villain, Jack Travis (Stuart Wilson), an ex-cop who sells heavy weapons to hoods, is not a fascinating supercreep, not after monster Gary Busey in LW and the whole South African diplomatic corps in LW2. And Leo Getz (Joe Pesci), the comedy hit of LW2 is now a pain in the neck with peroxide hair and about 687 too many “OK, OKs.” But Riggs does find true love with a cop named Lorna Cole. Played engagingly by supermodel Rene Russo, Lorna gives great kung fu and shares the movie’s funniest scene. As she and Riggs compare battle scars, they peel off their duds in a fever of passion-two lethal weapons who’ve found each other in a brutish world.

If this movie was being pitched in Robert Altman’s scathing Hollywood satire, “The Player,” it would be as a “comic Irish historical political romantic Western epic.” That’s just what “Far and Away” tries to be, and not surprisingly it dissolves into the non-sum of its dissonant parts. This $50 million-plus, 2-hour-and-20-minute movie, directed by Ron Howard, who wrote it with Bob Dolman, is a huge unwieldy vehicle for Tom Cruise. At this point in his career, Cruise is caught between being an actor (“Born on the Fourth of July”) and a commodity (" Days of Thunder"). “Far and Away” tries to fuse the two. The fuse fizzles.

Cruise plays Joe Donelly, a poor young illiterate tenant farmer in late-19th-century Ireland. As the movie opens we read a preface proclaiming the revolt of these hardscrabble farmers against their oppressive landlords. But this David Leanish promise doesn’t pan out. Instead the film moves into its John Ford phase, with Joe and Shannon Christie (Nicole Kidman), the rebellious daughter of the landowner family, thrown together on a voyage to America. In Boston’s Irish enclave Joe becomes a bare-knuckle professional fighter. But he can’t bridge the class gap with Shannon, and they’re pulled apart. In the climax, both find each other in the Oklahoma territory, racing for their piece of the New World in the Cherokee Strip land rush.

These formulaic bones might have shaped a classic with the right flesh. But " Far and Away" bounces off its various elements, never developing any depth in its characters or narrative. Looking for work in Boston, Joe is told: “We don’t hire Irish.” Why? As the homesteaders ride to stake their claims, there’s a two-second shot of Indians watching their land being stolen. Not enough. Joe and Shannon need to go through a lot of changes to come together; they simply don’t. Cruise as always is a winning presence; he and Kidman (now married) are as cute as two bees on a blossom. But you can’t make an epic out of the cutes.