When a senator comes up with a probation program to redeem criminals in the USA, the Supreme Court offers him a chance to prove the feasibility of his idea... by trying it out on the worst Old West villains ever: the Daltons. As usual, it’s up to Lucky Luke to keep an eye on the terrible four during their month-long trial period. If they can refrain from any crime during that time, they will be set free as good citizens...

Brothers Adolph and Arthur Caille are mechanical geniuses. They’ve just created one of the first slot machines and have presented it to their local senator, a notorious gambler. Much taken with the device, he agrees to send them on a tour of American cities to test the machine’s popularity. And, to escort them on this dangerous journey, he calls on his old friend Lucky Luke... So begins the wacky tale of how the one-armed bandit conquered the West!

While taking part in a rodeo in Wisconsin, Lucky Luke and Jolly Jumper meet Mario Bombardier, a Quebecois cowboy, and his mare the beautiful Province. It’s love at first sight for the two horses, and after the inevitable separation, Jolly Jumper can’t stop moping. Eventually Luke decides to head to Quebec in order to arrange a reunion – and discovers the merry atmosphere of the Nouvelle France: mounted police, bar fights, poutine, traditional French songs ... and an unscrupulous, wealthy banker...

Urgent message for the Dalton brothers: the president has approved a special measure to combat overpopulation in the country’s prisons. They’re going to be... hanged! Their last hope lies in a little known law that would see them walk free if they were to marry. A frantic Ma Dalton tries to locate brides for her boys, but their reputation precedes them, and the only candidates she eventually locates could well turn out to be a worse choice than the rope...

In this early adventure of the famous cowboy, Lucky Luke is dealing with one of the plagues of the Old West: quacks. “Doctor” Doxey is a con man, a charlatan who brews up useless elixirs and sells them as miracle cures for every ailment known to man. But he doesn’t stop at that and occasionally causes illnesses himself, the better to cure them—a behaviour that does not sit well with Luke...

Horace Greeley is heading west with his printing press and his rock-solid belief in the power of the press, printing issues of his Daily Star as he goes. But his insistence on publishing the truth isn’t making him universally loved. When Lucky Luke meets the quirky journalist, he agrees to help him settle in Dead End Gulch and protect him against those who would rather not see their dirty deeds in print.

After their umpteenth defeat at Lucky Luke’s hands, the Dalton brothers get into a big argument that ends with the four of them splitting up. They make a deal: Whoever is first to get a million dollars will be the leader of the gang. Going their separate ways, trying various schemes, each spreads his own kind of mayhem, forcing poor Lucky Luke to do four times the work to keep up with their antics !