After her mother's death Emily Dahl and her father move to a remote corner of Northern Norway. Devastated by grief, the darkness and cold in this secluded part of the world put Emily's nerves to the test. One day she explores an old, abandoned house where she finds a diary. Curious, she starts reading, only to soon discover the incredible story of a little girl named Mari. Every page uncovers more of Mari's tragic life. Emily wants to find out about Mari so she turns to her neighbor, Loar. From him she learns that Mari vanished without trace twenty years ago. With the help of the diary Emily tries to get to the bottom of Mari's secret, until one day she finds herself face to face with a girl in a white nightgown who claims that her name is Mari.