Geronimo Stilton is landing on the shores of the Americas for the first time. Accompanied by his younger sister Thea, cousin Trap, and little nephew Benjamin, Geronimo reaches Cactus City, an old western town. They are all excited at the prospect of experiencing the cowboy lifestyle, visiting a real ranch, riding, and cattle herding. However, what Geronimo was not expecting was their confrontation with bad guys, especially the evil sheriff of the town – Wicked Whiskers.In the hot and dusty environs of the Wild West, Geronimo and his gang face a showdown with the evil sheriff. The trip turns out to be a good adventure and Geronimo improves himself from being a wimpy mouse to a seeker of thrills.