After accidentally traveling through time in pursuit of the elder Stuart, Billy and friends find themselves lost in a land inhabited by giants: giant plants, giant animals, GIANT MONSTERS! Billy and his companions set off to explore the island, looking for fresh water and food. But a hailstorm forces them to take shelter in a grotto, where they find the trail of Billy’s grandfather, Virgil Stuart. However, following Grandpa’s footsteps turns out to be much more perilous than they expected.