Carl Thompson spends his days confined to a psychiatric ward for a gruesome murder he can’t remember committing. But his nights are spent elsewhere, patrolling an evacuated stretch of beach for some purpose that is not readily apparent.

During the day, he struggles to decipher which part of his existence is real and which is not. At night, he tries to uncover the mystery to a numbered code, a silver key, and a band of people who have given him his cryptic instructions.

Are these two realities linked? Could the answers to the mysteries in one reality be found within the other? Carl must find out before time runs out, and the sound of a shrill keening threatens to destroy both realities.