Sheldon Unger discovers that his grandmother is the tooth-fairy, and that the real job of the tooth fairy is to combat an ancient demon, the Tenebrion, which manifests as demented, fanged, dentures, which adopt a host and feast on fallen and live teeth. Of course, Sheldon finds this out after he accidentally frees the Tenebrion from his basement...and now it is up to him to find a way to stop it.