Four kids from suburbia on the hunt for lost pirate treasure discover a mystical amulet, The Star of the Mariner, that sends them back in time 300 years. Searching for the way home, they stumble across a group of treacherous kidnappers who give chase, swords drawn intent on insuring their silence. Captain Blood intervenes saving them, but they lose the amulet to the kidnappers in the ensuing melee. The kidnappers regroup and sail for the infamous pirate port of San Marie, located on a lush tropical island in the Bahamas. Once the kids enlighten Captain Blood on the kidnapper's plan to implicate him in the crime, they set sail for San Marie to clear his name and retrieve the amulet.
In San Marie, they split up, with the kids tracking down the amulet in the dusky taverns while Captain Blood rescues the kidnapped victim. When Captain Blood ventures into the village searching for the kids, the kidnappers, acting as false representatives of Her Royal Majesty, arrest him and schedule his hanging. The kids quickly conjure up a rescue plan, but have to wing-it when things go awry. With a little luck and some help from Mother Nature, they rescue Captain Blood only to lose the Star of the Mariner to a rogue pirate. With the island breaking up around them, Captain Blood rushes off to find the amulet while the kids take refuge in a nearby cave following the lead of a friendly, four-footed island native. After an avalanche barricades the entrance, they are forced to navigate the dark maze only to emerge through a secret time portal back into the future.