When forensic art conservator Clara Vance arrives on the isolated granite cliffs of Crow Island, Maine, her task seems simple: restore twelve final paintings left behind by the late, reclusive artist Julian Blackwood. Cut off from the mainland by a violent October nor'easter and a severed phone line, Clara unlocks Blackwood's north wing studio and makes a chilling discovery. Beneath the shroud of the twelfth canvas is a terrified portrait of her own face—and the oil paint is still wet. As she strips away the fresh layers under ultraviolet light, she uncovers hidden coordinates, a vanished predecessor,and a nineteen-year-old murder tied to her own forgotten childhood. Trapped on the island with a killer watching from the shadows of the Glass Lighthouse, Clara must unlock the secret of the thirteenth canvas before the midnight tide claims another victim.