Armed with secret knowledge, Juliette, now mayor of Silo 18 and her crew set out to rescue a world she hates but now understands better -- the world of the Silos with its rigid rules and terrible consequences for disobedience.

"In the underground city of Caverna, the world's most skilled craftspeople toil in the darkness to create delicacies beyond compare-- wines that remove memories, cheeses that make you hallucinate, and perfumes that convince you to trust the wearer, even as he slits your throat. On the surface, the people of Caverna seem ordinary, except for one thing: their faces are as blank as untouched snow. Expressions must be learned, and only the famous Facesmiths...

Thirteen-year-old Sully Stringfellow, his arch-nemesis Izzy Cisco, friend Moleman, and a league of long-forgotten plumber heroes team up to save Nitro City from mutant creatures in the sewers.

Pat O'Toole, his brother Coop, and their new companion, Kate, have narrowly escaped the cultlike community below New York City but must try to stop the cult's leader, Kate's grandfather.

When insane exile Corner and his army of mindless, whispering shadows invade Safe, a secret, underground community of freaks and disabled outcasts, Matthew, traumatized shapeshifter Ariel, and other misfits go to the dangerous place known as Above, where Matthew makes a shocking discovery about the histories entrusted to him.

"When Hyacinth Hayward tries to learn more about the magical rivers under London and how her family is connected to them, she stumbles upon a plot to steal the ancient stones that hold the city together"--

What waits Beneath? Pat O'Toole has always idolized his older brother, Coop. He's even helped Coop with some of his crazier plans -- such as risking his life to help his big brother dig a tunnel underneath their neighborhood in the suburbs of Washington, DC. Coop is . . . different. He doesn't talk on the phone, doesn't use email, and doesn't have friends. He's never really cared for anything but the thrill of being underground and Pat. So it's no...

Fourteen-year-olds Ananka Fishbein, Kiki Strike, and the other Irregulars encounter a Chinese mummy, a ghost, trained squirrels, and old enemies as they try to stop an art forgery ring and safeguard the secret streets hidden beneath New York City.

Nancy investigates an odd, possibly haunted statue and then tries to determine why thieves want an artifact that is hidden in the rubble of an underground ancient city.

"Thanks to the heroics of former New York City Mayor Tom Cafferty and his team, the world is once again safe. The villainous Foundation for Human Advancement has been dismantled, the cities of the world are safe from nuclear annihilation, and Cafferty is now on a hunt to decimate every nest of creatures on the planet. When Cafferty enters a nest underneath the Nevada desert, he is horrified to find it completely empty. It can only mean one thing:...