Eric Black has recurring nightmares following the recent death of his pregnant wife Rachel. Thinking he needs some space, he answers to a newspaper ad for work as a shepherd on a remote island in the Scottish Highlands. En route, he drops by his childhood home but is rebuked by his mother Glenys, who blames the death of his father on Eric's decision to leave them for Rachel, whom she implied to have been adulterous. Eric throws his wedding ring into a lake and breaks down after considering suicide. He and his Border Collie Baxter are then ferried to the island by the half-sighted Fisher, his only contact, who hands him a journal to record his thoughts. They settle into a dilapidated cottage by an unlit lighthouse. Eric finds a ring in a freshwater spring and, at the cottage, a shelf of journals identical to the one Fisher gave him. In one of the journals, he finds frantic writings about a witch on the island. At night, he struggles to climb the stairs to his room due to severe acrophobia.Strange events begin to occur. Eric wakes up the next day to see Rachel's old cup inexplicably filled with hot tea. After feeding the sheep, he sees Fisher entering the otherwise locked lighthouse and leaving the island in a hurry. One morning, he has a waking nightmare in which a demonic Glenys stabs him. When Baxter goes missing, he searches for him through heavy fog and finds an ancient luxury liner in a valley. On board, he picks up an old key and runs away after sensing the presence of a robed figure from his nightmares. While reading the journals, he finds a drawing of this figure, titled "The Wrecker", holding a lamp to lure a ship to a rock, and is startled to also find a drawing of Baxter. He later finds that the ring he plucked from the spring is the wedding ring he threw away.On the phone, Fisher implies that Eric is fated to be there as penance, making him confess that Rachel's death was due to his drunk driving. Desperate to be saved, Eric uses the old key to the lighthouse and, after an arduous climb, turns on its light to Fisher's dismay. As he exits, Eric finds his sheep ritualistically flayed and finds Baxter among them, but they all disappear the next day. When confronted by the robed figure, which takes on Rachel's guise, Eric immolates it and the cottage with the lighter Rachel gave him. Eric swims out to a boat but her ghost drags him underwater.Eric wakes up ashore and is taken to the police. When questioned, the full extent of his confession is revealed: due to drunk driving, the car carrying him and Rachel veered off to the edge of a cliff; taken over by acrophobia, Eric exited the car, causing it to be unbalanced and fall to the ocean with Rachel. Fisher phones Eric to say that while his penance for Rachel's death was over, she is angered that he broke the rules by escaping. It is shown that Fisher has killed Glenys using Eric's knife and planted his journal as evidence. Hearing the wind howl outside his interrogation room, Eric opens the door to see that he is emerging from the lighthouse back on the island. (thanks to Wikipedia)