Scotland, 1375: Muirteach MacPhee and his wife Mariota visit Edinburgh Castle, assisting the Lord of the Isles in his negotiations with King Robert II. A trading vessel arrives at the nearby port of Leith from the far away Norse settlement in Greenland. The ship brings unexpected diversion and carries coveted wares: gyrfalcons, unicorn's horns, and fine furs. Both King Robert and the Lord of the Isles desire the rare birds, easily worth a king's ransom.

Muirteach and Mariota, unaccustomed to the sophistication of castle life, initially find pleasure in the heady and flirtatious glamor of the royal court. Then sudden and unexpected cruelty, followed by the senseless death of a beautiful young girl, plunge the couple into a murky sea of alliances and intrigue that stretches from Scotland across the icy western ocean to the far northern lands of the Norse, leaving trails of treachery and murder in its wake.