Mulligan's Western circus - his troop, lion and elephant - arrive in town under the escort of Lucky Luke. Zilch, a rich businessman and organizer of the annual grand rodeo, thinks the circus is going to compete with his business and does everything to prevent it from putting on a show. He even engages killer-for-hire Rattlesnake Joe, but in the end his attempts will provide unexpected publicity for the circus. On with the show!