Rocky, Colt, and Tumtum, three young boys, along with their neighbor Amanda, are having a great time at the Mega Mountain amusement park. However, they soon encounter a group of evil warriors led by Medusa, who wants to take over the park and extort its owner. As Dave Dragon, a retired TV star, is holding his farewell party there, the warriors appear, and the children decide to thwart Medusa's wicked scheme.