Three children go with their author-father to a Maine Island. Not only are they enchanted by the rough beauty of the palace, but they are drawn into intrigue involving the treasure of an anti-blockade plot of the Civil War, and into a mysterious episode of threatened violence. But ten-year-old Amy, eleven-year-old Aaron, and twelve-year-old Allan are a match for the fishermen who molest their father's land, and in solving the mystery also bring happiness to the natives of Three-Part Island. A good adventure mystery which uses the details of Maine scenery, climate, and history to their best advantage.