A woman pleads for the help of Inspectors Frey and McGray. Her son received a death threat - right after learning he is to inherit the best part of a vast wine-producing estate. In exchange for 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. A mystery set in Victorian Scotland.