Kansas, 1896. After a tornado destroys the Gale family farm, eleven-year-old Dorothy goes missing. As the days pass, the Gales are increasingly terrified the worst has happened. But when the girl turns up unharmed four days later, the townsfolk breathe a sigh of relief. That is, until Dorothy herself relates her account of the events that took place during her disappearance.

In vivid detail, Dorothy describes a fantastical land and its magical inhabitants: a scarecrow, a tin man, a cowardly lion, a wizard, a witch. Her recollections are not only regarded as delusional, but also as pagan and diabolical in nature, especially when the body of a local spinster is found matching Dorothy's description of a witch she claims to have killed. Authorities find incriminating evidence tying Dorothy to the real murder, and they sentence Dorothy to the Topeka Insane Asylum.

When twenty-eight-year-old psychologist Dr. Evelyn Grace Wilford arrives at the asylum to interview Dorothy, she begins to wonder if Dorothy truly committed the crime or if something unfathomable has really occurred.

In a small town full of insidious secrets, Evelyn sets out to save Dorothy from her terrible circumstances, but can't help but fear whether something menacing may be lurking just out of sight.