Invasion of the Junkyard Hog (A Stepping Stone Book(TM))

Following Attack of the Shark-Headed Zombie and Stampede of the Supermarket Slugs is Bill Doyle's third tale of monsters and magic.
Mr. Cigam has a new job for Keats and Henry—a job working for his mixed-up stepsisters, Lillian and Beatrice. The sisters have lost a magical compass at the Tophat Junkyard, and ever since then, they've lost their sense of direction as well. Now they need pleh! (That's help spelled backward.) But for Keats and Henry, finding the compass isn't going to be easy. Something else is searching for it, too—a magic-sniffing junkyard hog with wings, long sharp tusks, and an appetite for destruction!