In the heart of the Maine woods, an experienced Appalachian Trail hiker goes missing. She is forty-two-year-old Valerie Gillis, who has vanished 200 miles from her final destination. Alone in the wilderness, Valerie pours her thoughts into fractured, poetic letters to her mother as she battles the elements and struggles to keep hoping.

At the centre of the search is Beverly, the determined Maine State Game Warden tasked with finding Valerie, who managing the search on the ground. While Beverly is searching, Lena, a seventy-six-year-old birdwatcher in a retirement community, becomes an unexpected armchair detective. Roving between these compelling narratives, a puzzle emerges, intensifying the frantic search, as Valerie's disappearance may not be accidental.