Bob, Grat, Bill, and Emmett Dalton were killed by Lucky Luke. Joe, William, Jack, and Averell, their cousins, want to avenge them but they are very poor gangsters. They decide to train intensively to become equals with their cousins, but mostly to compete with Lucky Luke. Joe Dalton asks our hero to join his gang to foam the country. Lucky Luke accepts to better control them, arrest them and bring them to Coyote Gulch prison for the first time.