After her father's sudden disappearance, thirteen-year-old aspiring detective Marietta travels to where his trail went cold, the town of Perdita, to ask for help. But with nobody believing her claim that something paranormal is to blame, her questions go nowhere. Determined to find out what happened--even if she has to do it alone--Marietta enters the nearby woods, where people are known to have vanished.

Armed with a peculiar magnifying glass that has the power to reveal lies and a mysterious letter containing clues about her father, Marietta stumbles into the alternate world hidden in the woods. There, she meets a friendly spirit who leads her to a phantom train where the Conductor says he'll help Marietta find her father--for a price. With the help of Wyatt Weiss, a mysterious boy with his own secrets, Marietta escapes without bargaining away something she can't afford to lose and finally learns where she's ended up: the Oddity Woods, an endless forest where monsters and ghosts roam freely.

Marietta and Wyatt work together to navigate the woods but become increasingly lost. A search for magical keys and solving a puzzling murder offer them ways to get home, but Marietta has yet to find her father...and the Conductor hounds her every step. Can she get what she came for and make a clean getaway, or will the woods claim another victim?