When Ruby woke up on her tenth birthday, something about her had changed. Something alarming enough to make her parents lock her in the garage and call the police. Something that got her sent to Thurmond, a brutal government "rehabilitation camp." She might have survived the mysterious disease that killed most of America's children, but she and the others emerged with something far worse: frightening abilities they cannot control. Now sixteen, Ruby is one of the dangerous ones.

Four years ago, Brynn left Saint Ambrose School following the shocking murder of her favorite teacher—a story that made headlines after the teacher’s body was found by three Saint Ambrose students in the woods behind their school. The case was never solved. Now that Brynn is moving home and starting her dream internship at a true-crime show, she’s determined to find out what really happened.

Pay close attention, and you might solve this. On Monday afternoon five students at Bayview High walk into detention. Bronwyn, the brain, is Yale-bound and never breaks a rule. Addy, the beauty, is the picture-perfect homecoming princess. Nate, the criminal, is already on probation for dealing. Cooper, the athlete, is the all-star baseball pitcher. And Simon, the outcast, is the creator of Bayview High's notorious gossip app. Only Simon never makes it out of that classroom. Before the end of detention, Simon's dead.

Milly, Aubrey, and Jonah Story are cousins, but they barely know each another, and they've never even met their grandmother. Rich and reclusive, she disinherited their parents before they were born. So when they each receive a letter inviting them to work at her island resort for the summer, they're surprised...and curious.

Ellingham Academy is a famous private school in Vermont for the brightest thinkers, inventors, and artists. It was founded by Albert Ellingham, an early 20th century tycoon, who wanted to make a wonderful place full of riddles, twisting pathways, and gardens. "A place", he said, "where learning is a game." Shortly after the school opened, his wife and daughter were kidnapped. The only real clue was a mocking riddle listing methods of murder, signed with the frightening pseudonym "Truly, Devious".