When Gregor falls through a grate in the laundry room of his apartment building, he hurtles into the dark Underland, where spiders, rats, and cockroaches coexist uneasily with humans. This world is on the brink of war, and Gregor's arrival is no accident. A prophecy foretells that Gregor has a role to play in the Underland's uncertain future. Gregor wants no part of it, until he realizes it's the only way to solve the mystery of his father's disappearance.

Chess has always been the protector over his younger siblings, Emma loves math, and Finn does what Finn does best - acting silly and being adored. They’ve been a happy family, just the three of them and their mom. But everything changes when reports of three kidnapped children reach the Greystone kids, and they’re shocked by the startling similarities between themselves and these complete strangers. The other kids share their same first and middle names. They’re the same ages. They even have identical birthdays. Who, exactly, are these strangers?

When Colin finds a shoebox full of letters hidden in a stranger’s attic, he knows he’s supposed to throw them away. That’s his summer job, getting rid of junk. But Colin wants to rescue the letters--and find out what really happened to best friends Rosemary and Toby way back in the 1970s. Meanwhile, across town, Nevaeh also finds a mysterious letter. But this one reads like a confession to a crime. And Nevaeh knows her father, the “Junk King,” expects her to join the rest of the family in blaming a single suspect: his business rival, Colin’s mom.

As the son of the world’s most famous tech billionaire, spoiled Jett Baranov has always gotten what he wanted. So when his father’s private jet drops him in the middle of the Arkansas wilderness, at a place called the Oasis, Jett can’t believe it. He’s forced to hand over his cell phone, eat grainy veggie patties, and participate in wholesome activities with the other kids, who he has absolutely no interest in hanging out with.

One minute they’re there: laughing and having fun at the house next door. The next minute, the teens are gone. Like magic. Marin can’t believe her eyes. Who are they? Can anyone else see them? What makes them so happy? Marin is lonely in this new town of hers and eager to figure out more. Then she meets Charley, who reveals that he knows about them, too. He calls them the “Remarkables”. Charley warns her to stay away from the Remarkables - and him.

Luke Garner has spent his entire life - all 12 years - in hiding. The government has outlawed families with more than two children. As the Garners' third child, Luke's very life is in danger. When Luke meets Jen, another "shadow child," he begins to question the government's policies.

For the past 12 years, adults called "Freds" have raised Rosi, her younger brother Bobo, and the other children of their town, saying it is too dangerous for them to stay with their parents - but now they are all being sent back. Since Rosi is the oldest, all the younger kids are looking to her with questions she doesn't have the answers to. She'd always trusted the Freds completely, but now she's not so sure. And their home is nothing like she'd expected, like nothing the Freds had prepared them for.

Jessie lives with her family in the frontier village of Clifton, Indiana. When diphtheria strikes the village and the children of Clifton start dying, Jessie's mother sends her on a dangerous mission to bring back help. But beyond the walls of Clifton, Jessie discovers a world even more alien and threatening than she could have imagined, and soon she finds her own life in jeopardy. Can she get help before the children of Clifton, and Jessie herself, run out of time?

Tim is just a peasant, but he dreams big. He wants more out of life than to grow up to be a woodsman like his father. Unfortunately, the only route to success in the kingdom of Wyld is to be born a prince. Still, Tim is determined. He is brave and clever and always tries to do the right thing—even though he rarely gets the credit for it.

Portico Reeves’s superpower is making sure all the other superheroes—like his parents and two best friends—stay super. And safe. Super safe. And he does this all in secret. No one in his civilian life knows he’s actually…Stuntboy! But his regular Portico identity is pretty cool, too. He lives in the biggest house on the block, maybe in the whole city, which basically makes it a castle. His mom calls where they live an apartment building. But a building with fifty doors just in the hallways is definitely a castle.

J.D. has a big problem - it's the night before the start of third grade, and his mom has just given him his first and worst home haircut. When the steady stream of insults from the entire student body of Douglass Elementary becomes too much for J.D., he takes matters into his own hands and discovers that, unlike his mom, he's a genius with the clippers. His work makes him the talk of the town and brings him enough hair business to open a barbershop from his bedroom.

Amari Peters has never stopped believing her missing brother, Quinton, is alive. Not even when the police told her otherwise, or when she got in trouble for standing up to bullies who said he was gone for good. So when she finds a ticking briefcase in his closet, containing a nomination for a summer tryout at the Bureau of Supernatural Affairs, she’s certain the secretive organization holds the key to locating Quinton - if only she can wrap her head around the idea of magicians, fairies, aliens, and other supernatural creatures all being real.

Sara Martinez is a hacker. She recently broke into the New York City foster care system to expose her foster parents as cheats and lawbreakers. However, instead of being hailed as a hero, Sara finds herself facing years in a juvenile detention facility and banned from using computers for the same stretch of time. Enter Mother, a British spy who not only gets Sara released from jail but also offers her a chance to make a home for herself within a secret MI5 agency. Operating out of a base in Scotland, the City Spies are five kids from various parts of the world.

Eleven-year-old Willodeen adores creatures of all kinds, but her favorites are the most unlovable beasts in the land: strange beasts known as “screechers”. The villagers of Perchance call them pests, even monsters, but Willodeen believes the animals serve a vital role in the complicated web of nature. Lately, though, nature has seemed angry indeed. Perchance has been cursed with fires and mudslides, droughts and fevers, and even the annual migration of hummingbears, a source of local pride and income, has dwindled.

Link, Michael, and Dana live in a quiet town. But it's woken up very quickly when someone sneaks into school and vandalizes it with a swastika. Nobody can believe it. How could such a symbol of hate end up in the middle of their school? Who would do such a thing? Because Michael was the first person to see it, he's the first suspect. Because Link is one of the most popular guys in school, everyone's looking to him to figure it out. And because Dana's the only Jewish girl in the whole town, everyone's treating her more like an outsider than ever.