Regan Fitz and Elliot Mason have been enemies since they started training to become Glitchers - people who travel through time to preserve important historical events. But everything changes when they find a letter from Regan’s future self, warning them about an impending disaster that threatens them and everyone they know.

Hank, Emerson, and their friends have returned to Camp Outlier for another summer of fun and shenanigans. Hank won’t let his RISK (Recurring Incident of the Strange Kind) factor of inconvenient invisibility stop him from having the best summer ever, even when it starts mysteriously turning people and objects around him invisible too. But between his invisibility and an internet celebrity joining their cabin, camp clown Hank is struggling to maintain his spotlight.

Berkeley and her best friend, Garth, live on an old cruise ship, scavenging for supplies from the drowned cities left behind on the ocean floor after the sea swallowed up all the land. They think they’ve seen every kind of aquatic creature, but they never expected to find sea monsters.... After awakening a Hydra, Berkeley and Garth are sent to live on a submarine, where they study and hunt sea monsters. But the Hydra wants revenge on their home ship - and if it succeeds, their families will go down with it.

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.

Meet Resilience, a Mars rover determined to live up to his name. Res was built to explore Mars. He was not built to have human emotions. But as he learns new things from the NASA scientists who assemble him, he begins to develop humanlike feelings. Maybe there’s a problem with his programming…. Human emotions or not, launch day comes, and Res blasts off to Mars, accompanied by a friendly drone helicopter named Fly. But Res quickly discovers that Mars is a dangerous place filled with dust storms and giant cliffs.