"It is Princess Harriet Hamsterbone to the rescue when Heady the hydra's egg is stolen, but her search leads her to a castle accessible only by a rat with a very long tail"--
Not only must Danny and Wendell trick-or-treat with skeptical classmate Christiana, school bully Big Eddy dares them to enter a haunted house on Halloween night, where they may have to sacrifice their candy to a ghost.