Thomas Ward has been John Gregory's apprentice for a year and a half and now it is time for Tom's six months training with another teacher, William "Bill" Arkwright. Saying goodbye to Alice for six months is hard enough, but a new teacher as well? That's really strenuous. "Having a different teacher gives you new knowledge and a new perspective," says John. And boy does it.
As soon as Tom arrives at Bill's house, he dives into learning about water witches, wights, and skelts. He learns how to batle with his staff and learns about Bill's parents, who are two ghosts trapped to the house Bill still lives in. Before long trouble arises and Bill and Tom are off to find the very Devil's Daughter, Morwena the water witch. Bill, a heavy drinker, gets drunk and is taken by Morwena.
Tom, a brave soul, goes off on his own to find Bill, but is soon accompanied by John and Alice. They go to a witch infested island and eventually recapture Bill. Though tired and weakened by the lack of food and water, he's okay. The Devil then stops time and forces Tom to face Morwena by himself, or so he thinks. Out of the woods comes Grimalkin, the witch assassin, and together they defeat Morwena and several other water witches.
What does Tom see in Alice that the Spook can't?