Profoundly evil powers with a global reach are gathering in the deepest recesses of an eerie castle in the Scottish Highlands. Gareth, a highly-intelligent young man facing the rest of his life confined to a wheelchair, arrives at the castle for a vacation with his troubled parents and their closest friends. Plunged into a terrifying ordeal, the extraordinary nature of the castle's strange secrets are brutally thrust on all of them. Gareth's sanity and the complex relationships surrounding him are challenged to breaking point in a supernatural game of cat and mouse as the world spirals into the greatest crisis it has ever faced.