With the help of the wizard Cadellin, Colin and Susan struggle to contain the forces of evil unleashed by the inadvertent awakening of the band of ancient horsemen known as the Wild Hunt.
Colin and Susan, who had been swept into the world of magic by the evil Morrigan as told in The Weirdstone of Brisingamen, are not safe from her revenge. A meeting with the Elf Lord in the woods on the Edge leads them back to Fundindelve and the wizard, Cadellin. The elves need Susan's bracelet of power, and against the advice of Cadellin she gives it to them. Without it she is in such danger that the only chance to save her is for Colin to invoke the Old Magic. He does so, but this unleashes an uncontrollable force, Garanhir the Hunter. The siege of Errwood, Susan's singlehanded fight with the Morrigan, and her final blast on the horn of Angharad Goldenhand are the climax of this haunting tale.
