The prolonged hospitalisation of Mrs. McClain forced Mary, her father and her brother back to a nomadic life aboard the a fishing boat which roamed the Alaskan waters of Cook Inlet and Eachemak Ray, in search of crabs. It was difficult for Mary to leave the town of Seldovia, her first real land home, especially hard to abandon dreams of a normal teenage life with her friend Annetic. Yet life aboard had its compensations. It gave Mary time to pursue her favorite hobby, sketching, and to discover her own little green paradise tucked off Hair Seal Bay. The accusation that the McClains are crab pirates comes as a terrific shock redoubled when old friends turn to enemies. Walt's real friendship replaces the flimsy variety offered by Annette and when the McClains rout out the true villain, Mary has learned an important lesson in human behavior, and the construction of a permanent home in her special paradise adds a final glowing touch. The subject boats, fishing, piracy usually meant for boys, should here find a female audience chiefly because of its interesting heroine.