When June's (Lindsay Burdge) mother goes mysteriously missing after diving in Spirit Lake, she and her sisters travel home to put her affairs in order. June, a mentally unstable documentary filmmaker, records the experience with her two half-sisters Annie (Jennifer Lafleur) and Isa (Aleksa Palladino). Their mother, an ecologist who was campaigning to preserve Spirit Lake, is gone but always present. As they settle back into her house, Isa takes up with June's ex-crush Josh (Ross Partridge) while several strange occurrences happen after they jokingly summon the ghost of a local legend. As the questions mount, the family begins to unravel and June finds herself drawn deeper into the true mystery of the lake.