The Curtis family looks for a house to rent in England while their patriarch Paul, a music composer, conducts an opera. The family is shown a secluded manor house owned by the eccentric Mrs. Aylwood, who lives in a small cottage on the property, set on the edge of a forest. While investigating the manor, youngest daughter Ellie Curtis is drawn to a bedroom overlooking the woods. Jan, the eldest daughter, looks out a window in the adjoining bedroom, and sees a blue glow in the forest as the window shatters. Mrs. Aylwood believes Jan is "sensitive" to signs, and decides to rent to the family.Jan feels that something horrible happened on the property and believes that someone is watching them from the woods, but her mother, Helen, dismisses the girl's concerns. However, the real estate agent reveals that Jan reminds Mrs. Aylwood of her daughter, who mysteriously disappeared many years ago. As the family moves into the manor, Jan carries a large mirror to the living room, and knocks over a telephone. After retrieving the phone, Jan looks back at the mirror, but does not see her own reflection. The glass cracks, revealing the image of a blindfolded girl wearing a white dress, and the mirror shatters.The next day, the girls visit a farm with puppies for sale, where they meet local teenager, Mike Fleming. In the barn, Ellie picks out a puppy while Jan and Mike talk. In a trance, Ellie writes "Nerak" on a foggy window, insisting it is the puppy's name. Mike's mother, Mary Fleming, approaches the barn and becomes upset upon seeing the name, which from the outside reads as "Karen."Later, at the manor, Jan waits inside while Ellie plays with puppy Nerak at the edge of the woods. After their parents leave for town, Ellie disappears and Jan finds her sister following Nerak. As they reach a pond, blue light flashes over the water and Jan sees a circle of blue beneath the surface. Another flash of blue light knocks Jan into the pond and a branch traps her beneath the surface. Mrs. Aylwood arrives and saves Jan from drowning.At Mrs. Aylwood's cottage, the girls learn that 17-year-old Karen Aylwood disappeared almost 30 years ago on the night of an eclipse. When Mrs. Aylwood discovered Karen was not in her room, she thought her daughter went to the pond, but Karen was not there either. The church bell rang and Mrs. Aylwood ran there, too, arriving just as a blue light struck the building. Three of Karen's friends, John Keller, Tom Colley, and Mary Pierce, ran screaming from the church as it caught fire. Mrs. Aylwood raced inside to save Karen, but she was not there. Karen's body was never found and the other teenagers did not know what happened, saying only that Karen was blindfolded as part of a game. Mrs. Aylwood admits that she hears whispers in the wind, and believes Karen is still in the woods.Another day or two later, the Curtis family attends a local motorbike race in which Mike Fleming competes, and Jan climbs onto a rock for a better view. Ellie plays with Nerak on a nearby sand-pile, but suddenly demands that her sister join her. A collision on the track starts a chain reaction and, as Jan reaches Ellie, a motorbike crashes onto the rock where she just stood. Ellie insists that Nerak wanted Jan to move.When Mike drives Jan home, she tells him about Karen's disappearance. She wonders aloud if Karen was murdered and still haunts the area. Jan mentions Karen's three friends, and a surprised Mike admits that his mother's maiden name is "Pierce" and that Tom Colley is a hermit living in the woods. Mike confronts his mother, who claims the teenagers were playing a game designed by John Keller when a summer storm arose and lightning struck, setting the church on fire. While three of the friends escaped, Mary believes that Karen ran away because it is the only logical explanation. Later, at the manor, Ellie shows Jan a viewer with which they can watch the eclipse that Saturday.The girls go horseback riding with Mike, but their horses spook and run off in two different directions. Mike chases Ellie, who is saved from death when a flash of blue light causes a truck driver to swerve off the road. Meanwhile, Jan's horse runs to the church, bucks her off, and runs away. Inside the church, a blue light flashes on a coffin and Jan sees the image of a blindfolded girl. She closes her eyes for a moment and the girl is gone, but a man appears. He chases her outside until she runs into Mike. As the man escapes, Mike realizes the stranger was Tom Colley. Jan leads Mike inside the church and a wind suddenly blows, shattering stained glass windows, and two disc-shaped shards, one bearing a solar image, fall into overlapping circles.That night, Tom visits John Keller's mansion and claims that he saw Karen alive in the church. Although Keller orders the hermit to remain silent on the subject, Tom wonders if Karen is back from the grave to haunt them. When Jan attends a carnival with Mike, she sees images of Karen, blindfolded, in the house of mirrors and mouthing "help me".Feeling Karen is trapped somewhere, Jan vows to discover what happened that fateful night. She visits Keller, but he refuses to speak. Jan finds Tom's shack and, once convinced that she is not Karen's ghost, Tom reveals that they were initiating Karen into their secret society on the night she disappeared. John blindfolded Karen and they encircled her, holding hands as they performed their ritual. In the middle of the ceremony, lightning struck and the bell fell. As Tom ran outside, he looked back but did not see Karen; she was already gone.Later, at Mrs. Aylwood's cottage, the old woman hears Ellie humming and brings out Karen's music box, which plays the same tune. As Jan shares the information gleaned from her conversation with Tom, a trance-like Ellie states that they must help Karen very soon. Mrs. Alywood believes Karen is speaking to them, but Ellie insists it is not Karen, and they must open the door. Ellie faints as her mother arrives. Despite the girls' protests, Helen insists on leaving, but the car stops working as they drive across a bridge. Jan forces them out of the car and off the bridge before lightning strikes and the vehicle falls into a ravine.The next day, Jan examines the eclipse viewer and realizes overlapping circles represent a solar eclipse. Jan telephones Mike and asks him to bring John Keller, Tom Colley, and his mother to the church before the eclipse so they can repeat the ceremony. Mrs. Aylwood learns of the plan and worries for Jan's safety.Inside the church, Jan takes Karen's place within the circle and orders Keller to repeat the ritual. Ellie enters, possessed by 'the Watcher'; a being from another dimension who exchanged places with Karen by mistake. The Watcher (speaking through Ellie) reveals that 30 years ago, the magnetic pull of the eclipse transferred their positions, but they can reverse the process with the same ceremony. Light and wind surround Jan, lifting her into the air, but Mike breaks the circle, grabs her, and they fall to safety as the eclipse occurs. Suddenly, Karen appears (having not aged a single day since time moves more slowly in the Watcher's dimension) and removes her blindfold as Mrs. Aylwood enters the church to welcome her daughter back home.