To escape Blake Sutton's army at the end of the enthralling The Well's End, Mia and her friends jump into the newly gurgling fountain of youth and swim to its very bottom. When they resurface, an astounding world awaits them - an entire underground civilization of humans, the Keepers of the Well. But instead of finding a safe haven, Mia and her gang are quickly embroiled in a dangerous, high-stakes battle royale.
Magic, adventure, and danger collide in an unsuspecting small town. Sixteen-year-old Mia Kish's small town of Fenton, Colorado, is known for three things: being home to the world's tallest sycamore tree, the national chicken thigh - eating contest, and one of the ritziest boarding schools in the country, Westbrook Academy. But when emergency sirens start blaring and Westbrook is put on lockdown, quarantined and surrounded by soldiers who shoot first and ask questions later, Mia realizes she's only just beginning to discover what makes Fenton special.