Teenager Megan, Elisabeth Harnois, still distraught over her twin sister Sophie's Elisabeth Harnois suicide, reluctantly agrees to join her friends on a summer trip to a lake house in the bayous of Louisiana. On the way, at a gas station, they meet Nick, Tyler Hoechlin, who provides the group with information on voodoo and other local superstitions.
As soon as they arrive at the house, Megan senses that Sophie's spirit might be trying to reach out to her, especially as a solstice — the moment when the realms of the living and the spectral feel closest — draws near. Megan goes running and trips, breaking a nail she had foreseen in several nightmares. Grumbling with a limp, she encounters a suspicious local, Leonard, R. Lee Ermey, who sits in his pickup and bears a wary stare toward the newcomers. In his cab, she notices a hat that looks identical to one Sophie had owned, an unsettling clue that deepens the sense of being watched.
The night before the solstice, Nick returns to the house for dinner. Megan explains to him the strange burden she carries — a key chain belonging to Sophie that keeps returning to her possession — and confides that she feels haunted by Sophie’s unresolved presence. The six friends later swim in the lake; Nick calls out for any spirits that might be present and, at his urging, Megan buries the key chain wrapped in a white cloth outside, hoping this ritual will expel the haunting. She then goes to take a bath and notices mud pouring from the taps, and suddenly the key chain reappears on the bathroom floor, intensifying the sense that something is meddling with them from beyond.
The following day, Megan visits Leonard’s house and stumbles into a young girl’s bedroom that appears to belong to a child who had vanished from the town years earlier. Newspaper clippings reveal that a girl named Malin disappeared, a fact that reframes Megan’s haunting. Realizing that it is Malin who is reaching out to her — not Sophie — Megan leads Nick back to the place where she tripped during her run, followed by Christian, Shawn Ashmore, who brings a gun for protection. The group becomes split, and Christian nearly fires on Nick. In a tense turn, Megan uncovers Malin’s body and discovers the key on Malin’s bicycle, a cryptic link to the girl’s burial. They promptly alert the local police to the grave discovery.
Christian finally confesses the truth: the year before, when the group visited the lake house without Megan, he and Sophie were driving and accidentally struck Malin. In fear of arrest, they buried Malin in the forest, and Sophie later killed herself under the weight of guilt. Malin’s ghost then materializes, and Christian bolts toward the road. Megan pursues him through the forest, but before she can reach him, a police car arrives and runs him down.
In the closing scenes, Megan stands by Malin’s grave, a quiet, reflective moment weighing the consequences of the past. Leonard comes home to find Malin’s key chain left on his porch, a sign that Megan’s actions have left a lasting mark. Ultimately, Megan and Nick decide to leave the town behind and start a life together in the city, seeking a fresh start away from the haunting memories that defined their summer by the lake.
