'STAND UP NOW,' SHE COMMANDED, HER VOICE SHARP. 'IT'S ALMOST TIME. THE MOMENT OF DANGER IS CLOSE. VERY SOON OUR ENEMIES WILL BE HERE.' 'ENEMIES?' I ASKED. 'IS THERE MORE THAN ONE?' 'OF COURSE, CHILD. THE FIEND'S DAUGHTER WILL NOT BE ALONE. SHE HAS CALLED OTHERS TO HER AID. WATER WITCHES FROM FAR AND WIDE ARE CONVERGING UPON THIS HILLOCK. THE STRUGGLE IS IMMINENT.'

As danger increases in the County, Tom is sent north by his master to be trained by Bill Arkwright, another spook. Arkwright lives in a haunted mill on the edge of a treacherous marsh and his training methods are harsh. He has toughened up many previous apprentices though and now he must do the same for Tom.

But when the Fiend sends his own daughter, a powerful water witch, to destroy Tom, Arkwright makes an error of judgement and Tom finds himself facing his enemies alone. The Spook and Alice hasten to his aid but will even their combined strength suffice in the face of such terrible dark power? And what is the Spook's mistake, the consequences of which might give final victory to the dark?