Tom is annoyed that the Spook won't allow him to leave the house, for fear that the fiend will get him. Alice is the same, wanting to do the grocery shopping instead of Tom. While the Spook is away, Tom goes to the village alone to get the groceries ignoring Alice's protests. On the way back, he is captured by a press-gang, a group of men who force boys into the King's army who are currently fighting a war. While tied up one night, Tom senses the presence of a dark force which takes the form of a malevolent witch, scaring the men away.
It is only when the witch comes close to him, that Tom realizes that it is Alice using a type of magic called Dread. Keeping this a secret from the Spook, they tell him that Alice got the men to chase her allowing Tom to escape. The Spook decides to send Tom to another Spook, Bill Arkwright, for further training. Soon they are on the way to Caster, where Tom is collected by a ferryman and brought to the boundary of Bill's home. Tom lets himself into the house to find that Bill has left to deal with business, leaving Tom a note saying not to harm the ghosts that live in the house.
Tom soon finds out the Bill is a drunk, he almost drowns Tom while teaching him how to swim, and beats him with his staff while teaching him how to fight. On top of that Tom is scared of Bill's two vicious wolfhounds Tooth and Claw . Having enough, Tom leaves in the middle of the night to return home after only the third day. Eventually he realizes that the dogs have been stalking him and Bill is waiting for him ahead. He gives Tom the letter that the Spook had sent to Bill. It said that after the treatment Bill gave previous apprentices, the Spook would never send another to him, but as the greatest threat to the Fiend, Tom is in danger and must learn to fight in order to survive, and Bill is the only one who can teach him that.
Tom returns to study with Bill, learning about water witches and improving his swimming. He then is sent to find a path through the marshes to reach an abandoned monastery. The dogs would be sent after him, and if he reaches the monastery first he wins. While running through the marshes he sees a woman in front of him, too late he realizes that it is a water witch. Using her bloodeye to paralyze him, she hooks his ear before dragging him into the marsh. Just in time, Claw saves him by biting the witches finger off. Back at the house, Tom learns that the witch, called Morewenna, is the Fiends daughter, and Bill has been hunting her for years. After Tom sends a letter to the Spook, he and Bill leave with the dogs to hunt for the witch. After speaking with a hermit, who has the ability to find anyone, they come to a village and lodge in a tavern. After eating and Bill getting drunk, they sleep for a few hours before heading towards the lakes. Bill becomes violently ill, and Tom with Claw, leave to look for the witch. After a while they return to find Claw's mate Tooth dead, and Bill's staff broken and boot floating in the water.
Back at the inn Tom uses a mirror to contact Alice to tell her of Bill's death. Afterwards he and Claw leave to return to Bill's house. They elude the witch chasing them and reach the house.
That night, one of the house ghosts, Bill's mother, tells Tom the he is still alive and is being held captive. The next morning, Tom goes to the river, where the ferryman is delivering salt to the house, he also has a letter for Tom from the Spook, saying that Tom must leave immediately for Caster. While the ferryman insists that Tom leave straight away with him, Tom goes back to the house first to check on the dog and get his staff. At the house, he finds Alice and the two return to the ferry. They soon realize that the ferryman is actually the Fiend. They are bait for a trap for the Spook, who manages to free them.
Later they are able to find Bill and rescue him with the unlikely help of the assassin witch Grimalkin. The Fiend later sends Tom out to fight Morwenna, holding the two Spooks and Alice's lives in the balance. Tom meets Grimalkin along the way who once again offers her help,to ensure the death of Morwenna, and Tom accepts but asks her why she is sure that the fiend will not turn up and kill everyone because she broke the rules. Grimalkin replies that she is the mother of one the fiends children and whoever births a child of the fiend is put under protection by him. It is revealed that Alice contacted her and asked her to protect Tom. After the battle is won Grimalkin asks Tom to visit her on Midsummers (according to tradition it that the midsummer after the 14th birthday that the son of a witch becomes a man) for a gift.
Learning that Alice has been using some witch powers, the Spook decides to bury Alice in a pit, but it is only with the persuasion of Bill and Tom, that he relents and banishes Alice to Pendle instead. Before she leaves, she gives Tom the blood jar containing Morwena's blood, so that he can protect himself, but he refuses to use it. Knowing it is unlikely she will see him again, she kisses him on the lips for a few seconds, before turning and running to Pendle. The Spook then departs and Tom finishes off his six months training with Bill.
On his way home the Fiend once again finds Tom. The Fiend tells him that Alice's mother and father were not her real parents, but rather he and Bony Lizzie are.