Following their father's gruesome murder in a violent home invasion, the Locke children return to his childhood home of Keyhouse in secluded Lovecraft, Massachusetts. Their mother, Nina, is too trapped in her grief—and a wine bottle—to notice that all in Keyhouse is not what it seems: too many locked doors, too many unanswered questions. Older kids Tyler and Kinsey aren't much better. But not youngest son Bode, who quickly finds a new friend living in an empty well and a new toy, a key, that offers hours of spirited entertainment. But again, all at Keyhouse is not what it seems, and not all doors are meant to be opened. Soon, horrors old and new, real and imagined, will come ravening after the Lockes and the secrets their family holds.