Hired by some lonely miners to bring them brides from the East, Lucky Luke is unaware that one of the women is Jenny, who has escaped from prison and is intent on joining her gang and robbing banks, starting with the one in Purgatory. After the gang attacks Luke's wagon train, Jenny is appalled at their behavior and impressed by Luke's. She decides to go straight and by the time they reach Purgatory, Jenny vows to be a perfect bride. She tries to stop her old gang from robbing the bank, but Luke thinks that she has joined them again... Hurt that Luke doubted her, she lets the gang tie him to a box of dynamite with a lit fuse...