The Spook's Mistake: Book 5 (The Wardstone Chronicles)

As danger increases in the County, Tom is sent far north by his master to be trained by Bill Arkwright, another Spook. But when the Fiend sends his own daughter, the ancient powerful water witch Morwena, to destroy Tom, Arkwright makes an error of judgement and Tom finds himself facing his enemies alone. The Spook and Alice realising his danger, hasten to his aid but will even their combined strengths 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?