The siblings are sent to the American West, landing in a dusty, deserted, abandoned ghost town in the 1870s. The town, named "Rattlesnake Flats," is eerily silent, giving the siblings a spooky feeling as they search for the next item required for their mission. They learn about the lives of cowboys and pioneers who settled the frontier. They are warned about a dangerous, notorious outlaw known only as the "Salty Dog," who they must avoid at all costs. Their mission requires them to decipher clues and search through the deserted buildings, including the saloon and the jail. As the sun begins to set, a sudden, powerful thunderstorm threatens the town, forcing a desperate, quick-thinking escape. They learn about the harsh realities and the lawlessness of the American frontier before returning to the tree house.
