Russell Mardell has fashioned a hugely original and totally terrifying folk horror noir from the rich ingredients of the Wiltshire countryside ... a land where both Dennis and Ben Wheatley meet and fear of the supernatural is only matched by the evil that men do. - Cathi Unsworth, author of Weirdo. Who is The Knock-Knock Man? A ghost, a killer, or the figment of a frightened boy's imagination? It is a question that continues to haunt disgraced New Salstone police officer, Ali Davenport, fifteen months after the devastating case that changed the course of her life. Now, after the death of her former colleague, Ernie, Ali has returned home to face a past that won't stay buried. Found in the disused office building where he worked as night security, Ernie's death has been ruled as a suicide. But not everyone is convinced. Wild stories are circulating about a supernatural presence in the building, an entity that might have attacked Ernie that fateful night. With the sale of the building about to go through, Ali is hired by its owner to work Ernie's remaining night shifts and debunk the potentially damaging story. An easy enough job, if you don't believe in ghosts. But then Ali meets Will, a teenage ghost hunter who claims to have evidence on film... Forming an unlikely partnership, Ali and Will soon fall headlong into a mystery that takes them through New Salstone's macabre history and into Ali's own dark past. As the pieces of the puzzle come together, Ali is forced to face the question of The Knock-Knock Man one last time. But what Ali doesn't know is The Knock-Knock Man has already been watching her for a very long time...