In the dim morning light, Orkney’s Skaill Bay is the backdrop for a calamity of nature’s making. When forensic scientist Rhona MacLeod joins the rescue efforts as a volunteer, she uncovers more than she bargained for: a human skeleton entombed in a stone crypt. The grave is believed to hail from the Viking Age, but Rhona’s analysis of the content points to more recent and sinister evil. And a shadow is thrown over the investigation when the skeleton is finally identified and unsettling connections emerge between the victim and the very people trying to solve. As forensic clues lead Rhona to a second, horrifying discovery, the question looms: how many more secrets are concealed in the sand?