"The Moon of Gomrath" is the name of the one night of the year when the Old Magic is at its most powerful. Had Colin and Susan known this, they would never have obeyed the strange compulsion that drove them to light a fire on the Beacon. But now it is too late, the band of ancient horsemen called the Wild Hunt are awake and on the ride, and no one is safe.

Colin is captured, Susan falls under the sway of the hideous Brollachan, and all along Alderley Edge the forces of evil rally for the conflict to come.

For there will be a battle, the likes of which cannot be imagined by mortals. And the outcome -- and all the hopes of the world -- depend on three unlikely champions: Susan, Colin, and their ally, the Wizard Cadellin.