A woman pleads for the help of Inspectors Frey and 'Nine-Nails' McGray. Her son, illegitimate scion of the Koloman family, has received an anonymous death threat - right after learning he is to inherit the best part of a vast wine-producing estate.

In exchange for their protection, she offers McGray a cure for his sister who has been locked in an insane asylum after brutally murdering their parents: the miraculous waters that spring in a small island in the remote Loch Maree.

The island has long been a sacred burial ground, but the legends around it will turn out to be much darker than McGray could have ever expected.