Returning from Greece, Tom and the Spook find that their home, including the Spook's precious library of knowledge, has been burned to the ground, and that their battle against the denizens of the dark must continue.

Tom is dismayed when his master the Spook decrees that they will be spending the winter on gloomy and forbidding Anglezarke Moor but soon discovers the reason for his master's decision, as they tangle with two dangerous witches and struggle to keep a dark mage from resurrecting an ancient evil.

As creatures of the dark hunt for the witch assassin Grimalkin, who carries the captured Fiend's head, Spook's apprentice Tom tries to find a way to finish this terrifying evil once and for all.

When witches steal Tom's inheritance and kidnap his relatives, Tom, the Spook, and Alice set out for Pendle Hill, a particularly dangerous district, in hopes of preventing the three witch clans from uniting to raise the Fiend, the Devil himself, thus bringing about an age of darkness.