Robert had been warned that fog often brought strange happenings. Aunt Abigail had told him often enough. But he hardly expected to meet a sea-going ghost, in charge of a Fog Boat, tying his craft to the fence at Sea House. This sea-going ghost, Captain McGinty, was discontent with his assignment from Davy Jones --collecting starfish, and washing them back out to sea. When Robert undertook to deliver Captain McGinty's letter requesting a transfer to Davy Jones, his mission took him through the Cave of the Winds to Davy Jones' Locker. En route Robert made a new friend -- Dimity, the daughter of a lighthouse keeper, whom Davy wanted for his own. Somehow the transitions from land-to-sea, from reality-to-unreality jolt the reader, so that he is glad to surface at the end of this deep sea saga.