Every night Lampie, the lighthouse keeper's daughter lights the lantern which warns the ships away from the rocks, but when the light goes out one night, a ship is wrecked and Lampie is sent to the Admiral's Black House in disgrace--there she finds and befriends the Admiral's son, who was born with a tail, and together they are pulled into an adventure of mermen and pirates, and secret identities long concealed but soon to be revealed.