Moy's best friend can't talk to her anymore. Her mother wonders if she's going mad. Her granny thinks that the evil fairy folk are after her. Moy can't believe it--all this just because she loves horses. When the horse that tried to kill St. Patrick visits Moy she has to help him win back his freedom. The only problem is that he can only leave the lake at night. If he's not back by dawn he'll die.