Truly Devious is a young adult mystery series by Maureen Johnson that follows the story of Stevie Bell, a brilliant student at Ellingham Academy, a prestigious boarding school with a dark secret.

The series begins with the disappearance of Ellingham Academy's founder, Dr. Edward Narracott, and his family in 1937. Years later, Stevie Bell arrives at the school determined to solve the cold case. With the help of her friends, David and Janie, she delves into the academy's history and uncovers a web of secrets, lies, and danger.

Each book in the series introduces a new mystery connected to the original disappearance, keeping readers engaged and guessing until the very end. The series is praised for its intricate plot, well-developed characters, and atmospheric setting. It's a must-read for fans of mystery, suspense, and young adult literature.

The five books in the series are:

1. Truly Devious
2. The Vanishing Stair
3. The Hand on the Wall
4. The Box in the Woods
5. The Final Story