Young Jonah Johnson and his family move into Mystic, CT. The town's local fisherman's son, Schooner, quickly befriends him and the two soon discover what seems to be a 300-year-old treasure map. The treasure of Captain Kidd that was lost in the town 3 decades earlier. While trying to evade the town's bullies, Jonah and Schooner keep their eye on Clive Steelway, a rich treasure-seeker who seems to have conniving plans for the treasure and the boys.