[2] The novel is set in Ireland and is told in present tense first person through Grubbs Grady, a child whose family are all chess players.

One night, he finds the mutilated bodies of his family and encounters Lord Loss, a gruesome human-like demon who sets his two familiars, Vein and Artery, on Grubbs.

As Grubbs begins to settle down, he meets and befriends Bill-E Spleen, another orphan who visits Dervish often to learn magic.

Later, when exploring the cellar, Grubbs comes across a book on demonology, and opens to a page containing an illustration of Lord Loss, which seemingly comes to life and calls to him.

Fearing for Grubbs’ safety, Bill-E eventually shares his theory that Dervish is a werewolf, as many Gradys were prone to lycanthropy, which manifests itself at puberty.

The only way to cure him is by winning three out of five simultaneous chess games with the powerfully magical demon master Lord Loss while another person battles his familiars.

While confronting Lord Loss, Dervish is constantly distracted from his chess match as Grubbs is unable to fight off the two familiars.

James Delingpole, writing in The Daily Telegraph described the book as dark but moral, "The scene in which the boy's father, mother and sister are disemboweled and shredded by the demon Lord Loss and his vile familiars Artery and Vein, must surely be the most jaw-droppingly grisly in children's literature.".