The beginning of the story is told through the eyes of Thomas Ward, and how a cloaked old man carrying a wooden staff in his left hand (as later it is found out from the spook himself that spooks tend to be left-handed) comes to the house. This man is the Spook. Spooks travel they're counties fighting troublesome creatures such as Boggarts, Ghosts/Ghasts, and Witches, for the money of the people who need these things gone. However the religious world hates them, for they are thought to be meddling in the dark powers themselves, which is against the Christian church.
Tom knows that his parents have agreed to make Tom the apprentice of the Spook. He will have to learn how the Spook fights "The Dark" as it's referred to in the book.
The Spooks is actually a caring man and always keeping an eye on his apprentice. He explains that most of his other apprentices have failed, due to them being cowardly, disobedient, or deceased. (Later in the series, we learn that a failed apprentice seeks vengeance on the Spook).
After learning what the Spook does, Tom is sent out on an errand to pick up some food for the house, (inside which lives a boggart, in whom the Spook has made a servant of sorts) suddenly some boys about the same age come up and threaten to beat him, unless he gives them some food. Tom refuses and the boys are about to beat him up, when suddenly a girl in pointy shoes shows up and scares them away by telling them a certain person has returned. She has an ungodly amount of strength for a girl of her age.
Her name is Alice Deane, and she is relative of one of the most dangerous witches in the County—Mother Malkin—and Bony Lizzie. Bony Lizzie uses bone magic, a type of necromancy involving the bones of dead people. Mother Malkin was one of the most sinister and powerful. She used blood magic, a type of witchcraft that involved draining the blood of anyone she thought could have useful features. She was called Mother Malkin for her strategy of welcoming young runaway women into a care home, and then sucking the blood of every girl there to make her more youthful. Over time she had developed a taste for children.
A long time ago the Spook had bound Mother Malkin to a pit in the ground with 13 iron bars on top, so she could never escape to terrorize anyone again.
Soon Tom is tricked by Alice to give Mother Malkin some cake, which (Tom doesn't know) is filled with blood. Mother Malkin becomes stronger and breaks out of her pit prison in two days.
Now it's up to Tom to recapture this witch. The Spook has been tricked by Bony Lizzie into going to Pendle (a place infested by witches and other creatures of the dark) and can not help Tom capture Mother Malkin. Tom gets the help of Alice, who is found to be unhappy with her family, and their dark ways, to defeat Mother Malkin. Later it is revealed Alice is a witch, and the Spooks isnt sure about her being with Tom...
The sequel, The Spook's Curse , and a third book, The Spook's Secret was released in July 2006. The fourth book of the series, The Spook's Battle was released on 5 July, 2007. The Spook's Mistake was released on 5 June 2008.
- On the back of each book is a warning that says, "Not to be Read After Dark."
- The book has been selected for the Lancashire Library and Information Service initiative Lancashire Reads; part of the 2008 National Year of Reading. The book will be promoted and distributed at venues across the county between September and November 2008.
- This book was the winner of the Hampshire Book Award. Joseph Delaney attended the event and met the pupils who voted for his book.
- The haunted house in which Tom is told to stay in until midnight and then head for the cellar by the spook is 'No 13 Watery Lane', is based on the house in which the author Joseph Delaney once lived in as a child, which was really called 'No 1 Water Lane'. He and his brothers had the same dream where a shadow-thing named 'Sam' would leave its place from underneath the stairs and carry Joseph down into the darkness.
- A film adaptation of the book was announced on March 18, 2008 and will be directed by Kevin Lima set to release sometime in 2011.