In New York City in 1880, the Dalton brothers — Joe Dalton, Jack, William, and Averell Dalton — escape a court trial tied to their bank-sales cousin's disgrace and run riot, plundering several banks across the city as they go. On their trail is the famed lawman Lucky Luke, who keeps a careful eye on their movements and eventual schemes to stay ahead of the law.
After a frantic escape, the Daltons backtrack to Central Park to retrieve their loot, only to stumble onto a caravan of immigrants bound for California. The caravan’s leader, Piotr, explains they have 80 days to reach California and claim their land; but a scheming duo—Crook and Bartleby—is trying to sabotage the sale and keep the money that was paid in advance. Faced with a choice between a safer, longer route and a faster, riskier path, the Daltons find themselves aligning with the immigrants’ push for a quicker voyage, even as Crook and Bartleby lay traps to derail the journey.
To move faster, the group sets off on an unsafe route through Hole Gutch, crosses the Deadly Desert of Death, and presses on past the territory of the Crazy Wolves. Among the new settlers are a Chinese chef couple, a teacher named Miss Littletown, a loudmouthed mule driver, and a barber, all aiming for a fresh start in California. Along the way, Crook and Bartleby intensify their sabotage, but their efforts prove ineffective against Luke’s determined pursuit and the caravan’s resolve. Crook even attempts to aid the Daltons at one point, only to be rebuffed by Joe once the hidden loot inside the wagons is discovered. Meanwhile, Averell’s antics surface in a chaotic, comic rain dance sparked by a cockroach in his shoe, a moment that adds humor amid the mounting tension.
As they close in on California—within 24 hours—the danger sharpens. Crook unleashes one final ruse: a cannon from the circus to blow up the canyon bridge. To counter this, Miss Littletown proposes turning several wagons into hot-air balloons and soaring over the obstacle. The plan works for a stretch, and the caravan presses on toward California, only to learn the land beneath their feet is an old gold mine.
The settlers reveal a harsh truth: the promised land hides little more than a forsaken mine, and Crook’s manipulations have left many settlers misled. Joe promises payment from the loot hidden earlier, but Averell has already uncovered and stashed the treasure in their ball-and-chains, shifting the loyalties and igniting conflict among the group. The Daltons flee into the abandoned mine, triggering a high-stakes roller-coaster chase that snakes between the settlers, Luke, Rantanplan, and Crook. Luke proves his nerve, saving Miss Littletown and her students, while the Daltons are eventually cornered and defeated.
In a final twist, Crook arrives with dynamite, demanding the loot back from the Daltons. Rantanplan somehow triggers a mega explosion that destroys the stolen loot and exposes gold beneath the land, turning the settlers’ grim disappointment into a surprising windfall for the community. The climax ends with justice closing in on the culprits as Lucky Luke ties up the Daltons, Crook, and Bartleby, sending them off toward their overdue reckoning as the sun sets on the horizon.
