On their way to Kirrin Island, George shows her cousins a shipwreck, explaining it was her great-great-great grandfather's ship. He had been transporting gold when the ship was wrecked in a storm, but despite divers investigating the wreck, the gold was never found. After visiting the wreck, the five arrive on the Island and are exploring the ruined castle when a huge storm blows up, making it too dangerous for them to return to the mainland. While they take shelter on the island, the sea throws up the old shipwreck, grounding it on the rocks surrounding the island. Excited by these developments, they decide to come back at dawn the next day to investigate the wreck before it is discovered.