In one vast and sparkling city, everyone can fly - well, almost everyone. A few, nicknamed leadfeet, are sentenced by a trick of nature or fate to forever spend their lives closer to the ground. But one night, a girl named Gurl -- a leadfoot, an orphan, a nobody -- discovers that she can do something much better than fly. She can become invisible. This amazing power will help her uncover the secret mysteries of the city. But even with her newfound talent, Gurl can't seem to hide from a giant rat man with a taste for cats, a manipulative matron with a penchant for plastic surgery, and a belligerent boy named Bug. Gradually Gurl learns to control her power and teams up with Bug to figure out who and what she is. Their quest will take them on a wild ride through this magical city, where they'll confront chatty birds and mind-bending monkeys, an eccentric genius with a head full of grass and a pocket full of kittens, and the handsome but lethal Sweetcheeks Grabowski -- the gangster who holds the key to Gurl's past ... and the world's future.