Things are hairy in River Heights this holiday season. Two wolves have disappeared from WildWolf, the federal wolf preserve just outside of town. Local farmers think the missing wolves are killing their sheep, but there are also rumors of werewolf sightings nearby. At the same time, the annual River Heights Winter Carnival is set to begin. When the first two days of the outdoor festival are full of tragic disasters, Nancy can't help but wonder—is there a link between the carnival's trouble and the missing wolves?

After the carnival's beautiful ice palace is destroyed, Nancy's sure there's a wolf at River Heights's door. But is the leader of this pack of crimes human, or beast?