Thirteen-year-old Moon Rains battles a relentless and mysterious illness. In a desperate quest for a cure, her mother takes her to the isolated Clearlake Institute on a remote Scottish island, a place rumoured to hold innovative treatments. During their train journey to Clearlake, Moon and her mother encounter a cryptic woman who delivers a chilling message. As Moon arrives at Clearlake, she discovers a place cloaked in secrets and shadows. Darkened halls are prowled by ghastly old witches, eerie eyes watch their every move, and children endure harrowing procedures. With the help of newfound friends, Moon embarks on a perilous journey to uncover the sinister mysteries that shroud Clearlake. One room, in particular, hides an unspeakable secret: children who enter it, vanish without a trace. Haunted by the enigmatic woman's warning: “Do not go into Room 217,” Moon and her friends race against time to escape Clearlake's sinister grasp. Will they make it out before it's too late?