Edison Beaker, creature seeker. 2, The lost city

"After escaping evil Baron Umbra, the sticky Underlings, and other creepy creatures of the Underwhere, Edison Beaker and his young sister, Tesla, are safe at home. And then their creature friend Knox comes calling. She needs help--back on the other side of the Night Door. Edison desperately wants to follow family tradition and become a true Creature Seeker, protecting the world from monsters and mayhem. So what else can he do but follow Knox? (Wi...