On the island of Chincoteague, siblings Paul and Maureen Beebe dream of owning a wild pony from the neighboring island of Assateague. Their chance comes when they see a beautiful mare, the Phantom, who has always escaped capture, swimming with her newborn foal, Misty, during the annual Pony Penning Day. The children work hard to buy both horses, facing challenges of training, responsibility, and ultimately making a difficult choice about freedom versus companionship. This classic story is based on real events and celebrates the bond between humans and animals, and the wild spirit of the legendary Chincoteague ponies.