In the third volume of this middle-grade series, Drew Weing delivers a fresh and funny take on the age-old battle between kids and closet-dwelling monsters. As the assistant to Margo Maloo, Charles has gone on assignment in some pretty interesting locations. He's been to a vampire's lair, an ogre's den, and even a monster grocery store! But he's never been to Downside, Echo City's underground monster metropolis that is super mysterious and DEFINITELY off limits to kids. But a settlement of giant spiders is about to be dynamited by unwitting construction workers—and, coincidentally, one of those giant spiders "accidentally" bit Charles. His cure and the spiders' salvation lie in the Downside—if Charles and Margo can make it in time.