After more than a decade of tending to small children on a failing farm in rural Tennessee, oppressed by poverty and isolation, Dellarobia Turnbow has mitigated her boredom by surrendering to an obsessive flirtation with a younger man. As she retreats to a secluded mountain cabin for an intended tryst, she instead encounters something on the mountainside she cannot explain or understand: a forested valley filled with a lake of silent red fire that appears to her a miracle. In reality, the forest is ablaze with millions of butterflies. Her discovery of this phenomenon ignites a media and religious firestorm that will change her life forever.