Harrison is a lonely teenager, terrified of the ocean since a childhood sailing accident took his father - and his right leg. One of the "sensitives" who are attuned to the supernatural world, Harrison and his mother have just moved to the worst possible place for a boy like him: Dunnsmouth, a Lovecraftian town perched on rocks above the Atlantic, where monsters lurk under the waves, and creepy teachers run the local school. When Harrison's mother, a marine biologist, disappears at sea, his attempts to find her puts him in conflict with a strange church, a knife-wielding killer, and the Deep...