Tia and her pony Gable are inseparable. When her father proposes a visit to a remote island to research the ancient legend of shipwrecked horse, Tia is reluctant until she realizes that Gable can come, too. Riding alone on the cliffs of the island, Tia meets a dark rider on a dark horse, who turn out to be an island-born teen, Daniel, and his amazing island horse, Harley. Daniel and Tia hit it off and spend days riding together. Daniel introduces Tia and Gable to the joys of swimming in the ocean, as well as honing their cross-country jumping skills. Elsewhere on the island, though, events take on a sinister pattern as the story of the shipwreck emerges and Tia’s father seems to be closing in on the mystery of the island horse. Soon, Tia and Gable must fight not only the awesome power of the sea but combat the evil human force that threatens their existence on the island.