On a remote island cut off from the mainland, an old rule keeps everyone inside after dark, because once the sun goes down, no one casts a shadow anymore. Mara Whitlock always thought it was superstition, until she notices something the others have missed. The shadows are not just vanishing at sunset, they are vanishing earlier and earlier, slipping away from their owners minutes before nightfall. And every person whose shadow leaves first is never seen again by morning. As Mara digs into the island's buried history alongside Ethan Blackwell and Daniel Cross, she realizes the missing shadows are not a symptom of something wrong with the island, they are a warning. Something out there has learned to take the shadow first, and the person always follows.