Levy's little-girl sleuths Gwen and Jill are in their element when Halloween week finds their school beset by spooky sounds and eerie phenomena. History teacher Mr. Murdock tells reporters there are legends of a werewolf on the site, and so it's no surprise when the werewolf the girls flush out at the school costume party is revealed as Mr. Murdock himself--stirring up rumors so he can write a best-selling book about the haunting. The situation provides some atmospheric background for the girls' mildly suspenseful investigations; and Gerstein has a ball from start (with a funny spread depicting eleven possible Halloween costumes for basset-hound Fletcher) to Finish, with vampires Gwen and Sill chasing the werewolf through an assembly of costumed monsters and a tubby scowling principal in shorts and Viking horns dismissing Mr. Murdock. The lemonade-stand story involves a more typical, tepid mystery: someone is sabotaging Gwen and Jill's business by spiking their fresh-squeezed lemonade with white pepper on one occasion and goldfish on another. Again, the culprits (rival kid merchants) are the ones suspected all along; but Levy throws in enough curves to keep readers in doubt.