Somewhere in Spain, off-road race car driver Ben [Bud Spencer] eagerly anticipates the next rallycross, driven by the prize: a striking red Puma dune buggy with a yellow top. His rival, the sharp and fearless Kid [Terence Hill], shares the same dream and eyes the same prize with a competitive spark. The race roars to life, and in a dramatic finish the two cars surge toward the buggy at the same moment, ending in a tie that awards them both the vehicle.
Sharing the glory proves impossible, so they set out to decide a fair fates pattern. What starts as a playful dispute soon spirals into a sequence of dares: a high-stakes card game, a tense arm-wrestling match, and finally a boisterous “beer and hot-dog” eating contest in the funfair pub, where the first one to give up loses the car and picks up the tab. The contest is lighthearted at first, a rough-and-tumble wake-up call to see who truly deserves the prize.
Their competition is interrupted by men working for The Boss, a ruthless building profiteer who wants Luna Park torn down to make way for a skyscraper. The Boss’s men tear into the pub and threaten the customers, and Ben and Kid refuse to back down. They escape in high spirits, but not before the buggy is rammed by a rival car, leaving them determined to reclaim a new ride.
To regain ground, the two barge into the Boss’s restaurant during a dance party and demand replacement for the stolen buggy. The Boss wavers, but the German-born Freudian psychologist known as the Doctor [Donald Pleasence] pushes the Boss toward a hard line, insisting that giving in would create bad psychological fallout and accusing Ben and Kid of acting like spoiled children who need a father figure. The Doctor’s taunts goad the Boss into ruthless action, and he sends his henchman Attila [Deogratias Huerta] after them, even spraying gasoline on Ben’s car and setting it aflame—only for the duo to extinguish the blaze by racing into a nearby car wash.
Undeterred, Kid works to persuade the Boss to hand over the dune buggy, and Ben reluctantly follows, partly to scout for a possible choir assignment he’s been eyeing. The first attempt ends in a brutal brawl in the fairgrounds’ gym, where Ben and Kid defeat Attila and his henchmen. Enraged, the Boss unleashes a motorcycle gang, triggering a chase through a forest that the two manage to outmaneuver.
The Doctor persuades the Boss to unleash Paganini [Manuel de Blas], a feared assassin from the Chicago Underworld, after the two rivals. Paganini confronts them, but they manage to evade his relentless pursuit. Kid lures the assassin away from Ben’s place to the auditorium where the choir rehearses, igniting a clash in the middle of a work session that ends with Ben being kicked out, while Paganini is forced to stay and play violin at the Boss’s restaurant as a bizarre punishment.
The Boss’s attention shifts to Jeremias [Luis Barbero], Ben’s loyal assistant and a former cook who once worked for the Boss. Jeremias is found beaten in his garage, and Ben heads straight to the Boss’s restaurant to confront him, forcing his way in alongside Kid and mounting a full-blown struggle with the Boss’s henchmen.
In the end, the Boss tires of the escalating war and offers not one, but two dune buggies—one for each of them. The pair celebrate their hard-won victory, but a distraction ties into Kid’s interest in Liza [Patty Shepard], causing him to crash and destroy Ben’s buggy. As the two stand amid the wreckage, they pause to decide how to divide the remaining prize and what the future holds for their unlikely, stubborn rivalry.
