Like the author's other books (Half a World Away, The Roaring '40's), this one takes place in the envious of Tasmania. Specifically it's a yacht The Timmari cruising around the East Coast. On board are two father and son teams--the Ironns and the Roxtells. Of special interest is Tasman Island, popularly called Haunted Island, a sheer rock cliff, almost impossible to approach. Not to this crew, though. And when they land they find they've been preceded--by Mr. Roxtell's long-lost sister, her best friend, and a whole settlement comprised of the members of a small Scandinavian religious sect. The shifting in time and place, as the story leaps back and forth from The Timmari to recount the girls' adventures, makes the course almost impossible to trace. The local patois lends to the total incomprehensibility.