Marina, a city girl, and her brother spend a few summer days at their grandmother's house. There they discover that their grandmother is a pirate in the 21st century, and that she plans to rescue her husband from an enchanted island that appears one day every forty years, using a magic bottle. One night, Ulysses is kidnapped and the bottle is stolen by a bloodthirsty pirate, who intends to take a great diamond from the island. From here, Marina, along with her grandmother and her crew, begins a chase against the clock, facing terrible pirates and countless dangers, to rescue Ulysses, recover the bottle and reach the island in time to save her grandfather.