Avery Grambs has a plan for a better future: Survive high school, win a scholarship, and get out. But her fortunes change in an instant when billionaire Tobias Hawthorne dies and leaves Avery virtually his entire fortune. The catch? Avery has no idea why - or even who Tobias Hawthorne is. To receive her inheritance, Avery must move into sprawling, secret passage-filled Hawthorne House, where every room bears the old man's touch - and his love of puzzles, riddles, and codes.

Welcome to the Grandest Game, an annual competition run by billionaire Avery Grambs and the four infamous Hawthorne brothers, whose family fortune she inherited. Designed to give anyone a shot at fame and fortune, this year’s game requires one of seven golden tickets to enter. With millions on the line, those seven players will do whatever it takes to win. Some of the players are in it for the money. Some for power. Some for reasons all their own. Every single one of them has secrets.

Seventeen-year-old Cassie is a natural at reading people. Piecing together the tiniest details, she can tell you who you are and what you want. But, it's not a skill that she's ever taken seriously. That is, until the FBI come knocking: they've begun a classified program that uses exceptional teenagers to crack infamous cold cases, and they need Cassie. What Cassie doesn't realize is that there's more at risk than a few unsolved homicides—especially when she's sent to live with a group of teens whose gifts are as unusual as her own

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".

When Sawyer Taft agrees to move in with her grandmother, she expects some things to be different, but what she doesn't expect is to get sucked into a group of over-privileged, yet somehow lovable debs who have kidnapped one of their own in hopes of blackmailing her into keeping their secrets under wraps - secrets that are far bigger and more scandalous than anyone could have imagined. As Sawyer works to uncover the identity of her father, she must also navigate the twisted relationships between her new friends and their powerful parents and help them discover the villain among them.