American Donal MacCraith is on a road trip along the western coast of Scotland to the Western Isles. His family roots are there, but his main reasons for the extended vacation are the songs and legends. He's a folk-singer, come to collect some new old material. In Stornoway he meets the Shielingers and Niall MacLachlan. When he continues his exploration of Lewis, making for the small crofting community his grandmother left as a young woman, he finds Niall waiting for him on the road just outside the town.
Once out on the road, Niall makes a play for Donal, and they begin a casual no-strings relationship, though Donal senses Niall has an agenda of his own. He's right, and the clue is in the old family stories of the Sinclair Selkie Donal's grandmother had told him. That clue will lead Donal to the startling truth behind the legend, and he and Niall will be faced with life-changing choices.