The film begins with Bambino (Bud Spencer) walking through the desert. He sees some smoke from a campfire and goes to see who it is. He finds four Denver convicts and steals their beans and horses. He also knocks a guy out with one blow to the top of his head. When the guy awakens he has become addlepated and becomes a running gag throughout the film. Then the film starts the opening credits and the title song. You see Trinity (Terence Hill) on his travois with the horse pulling it. He wakes up and sees the exact same fire Bambino saw. The convicts are trying to fry some more beans. Trinity pretends to be an innocent lackwit, even advising the convicts to try to snap their addlepated confrere out of it by hitting him on the head again. When this doesn't work the other convicts decide to punish the "kid' by just "winging" him, but Trinity displays his superior gun skills. Trinity steals the beans and tricks them into fighting each other to see which one he doesn't shoot. He leaves them fighting.
Then we go and see Bambino at home getting a bath. His father sees Trinity and they both go inside. Bambino is furious to see Trinity because in the last film Trinity had given a thirty-horse herd away. Trinity takes a very quick bath and everyone goes to the table for lunch. Then the four convicts come and try to get Trinity and Bambino, but Trinity's mother sneaks around from the back entrance and ushers them out with a shotgun. That night, Trinity's father has some kind of an attack. He makes Trinity and Bambino promise to work together. When Bambino leaves the room, it is revealed that his dad was faking it. Bambino is forced to teach Trinity how to be a successful horse thief. They see a wagon with two tired mules who are not moving and go to try and rob the passengers. All they find instead is a family with a farting baby and a young girl Trinity falls for. The family isn't moving because a wheel broke and they can't change it because the wagon is too heavy. Trinity and Bambino end up helping the family. When Trinity and Bambino arrive in town, they head out to the local saloon.
Inside Trinity, Bambino and two other cowboys play a card game with a professional card sharp named Wild Card Hendriks. Thanks to his cardsharping skills, Trinity deals everybody a potentially winning hand, but his is a little bit better so he wins, but he is accused of being a cheater. Trinity and Wild Card get a drink because Wild Card says a bullet hurts less with some alcohol in your system. While Bambino (with a couple of well-placed thumps on the head) keeps the other two from interfering, Trinity draws his gun, holsters it while Hendricks is looking and slaps him in the face fifteen times before a bewildered Wildcard leaves unavenged. He tries to shoot Trinity from behind but gets shot in the hand by Trinity. Trinity and Bambino each get a suit with the winnings, then run into the same family they helped earlier. They lie to them, saying they are federal agents. Then they go into a club restaurant and buy some food while they drive the waiters insane by consuming huge helpings of food. When they leave the meet a man who gives them four thousand dollars to "keep their eyes shut", thinking them to be federal agents (word has gotten out of the lie they gave the family from earlier). Then they hide on the side of the road to wait for some horses but run into the exact same family as they did before. They have a nice little dinner and part ways for a while.
The two brothers then travel to San Jos[disambiguation needed]. They go into a bar and start a brawl. They arrest some convicts and take them to the sheriff (for a bounty). The sheriff informs Trinity and Bambino that everyone in San Jos works for the man who paid them the four thousand dollars. The brothers go to the mission because the sheriff tells them they should not go there. There they find that the man who paid them off also has men who use the mission to store stolen loot. The brothers try to trick the monks by helping them beat the outlaws, then take the loot. After a seven-minute long fight, a group of Rangers show up and one of them thinks he recognizes Bambino as a wanted horse thief. To allay his suspicions, Trinity gives him the stolen loot. The brothers escape and run into the family again, and the film ends.