Gretel, yes, that Gretel, is now all grown up and working as a private investigator in 18th century Bavaria. Her professional interest is piqued when she begins to hear whispers of mysterious goings-on off the coast of Schleswig-Holstein: sailors are disappearing, and there are rumours of mermaids and sea creatures and all manner of slippery, sea-based happenings. Ordinarily, Gretel's interest in sea-life does not extend beyond that which is edible,...