On a dark night, when two siblings, Lacey and Willy, are caught spying on their mother as she covers her lover's face with a black silk stocking, the abusive lover binds Willy's hands and feet to a bed and puts a gag in his mouth. Willy cries and struggles, while Lacey grabs a carving knife from the kitchen and cuts her brother free. As mother and boyfriend make love in the bedroom, Willy plunges the knife into the lover's back, killing him.Twenty years later, the adult Lacey (Suzanna Love) and Willy (Nicholas Love) attend church. Lacey confesses to Father Reilly (Llewelyn Thomas) that she is still haunted by the memory the murder and he encourages her to pray. Lacey and Willy live on a farm with their aunt and uncle, Helen (Felicite Morgan) and Ernest Edwards (Bill Rayburn). When Father Reilly pays them a visit, Willy (having been mute since "that night"), who works as a farmhand, greets the priest with a handshake.At dinner, Lacey reads a letter from her mother, who wants to see her children before she dies. Willy abruptly leaves the table and Lacey follows to reassure him that he is not responsible for an event that happened so long ago. Back at the table, Lacey is uncomfortable as her husband, Jake (Ron James), carves a chicken with a sharp knife. She picks out a bottle of wine from the pantry and it reminds her of the liquor bottle her mother held the night of the tragedy. After dinner, Willy burns his mother's letter.That night, Lacey has a nightmare of being bound to a bed and gagged, and wakes in a sweat. She asks her husband for help. Lacey and Jake visit Dr. Warren (John Carradine), who hypnotizes her to be able to understand her trauma. She revisits the memories she has suppressed, but at the point where Willy kills her mother's lover, Lacey's voice becomes a series of guttural demonic sounds. Dr. Warren brings her out of her trance, and recommends that she visit her childhood home to confront her fear.After Lacey and Jake leave on their journey, Willy's nerves are rattled and he paints the mirror in the barn black. Later, Aunt Helen discovers that Willy has also painted the mirrors in house black. When she asks him why, he cannot give her an answer.A "for sale" sign is posted at Lacey's former house so the couple introduce themselves as home buyers to the three children in the house -- Jane (Jane Pratt), Susan (Lucinda Ziesing) and Timmy (David Swim). The house is bright and cheerful. Lacey enters the master bedroom, which is empty except for a mirror, casting the reflection of her mother's lover whose face is covered in a black stocking. However, no one is in the room with her, and she hurls a chair, smashing the mirror. Jake makes apologies to the children, and the couple leaves with the mirror frame and shards of broken glass.At home, Jake glues the mirror back together and hangs it on a kitchen wall. However, one shard of glass has been left behind, and the lover's evil spirit is released. The invisible spirit attacks Susan and forces her to gouge herself in the throat with a pair of scissors. Timmy's neck is snapped when he climbs in the bathroom window to surprise her. As Jane picks up the glass shard, it radiates a powerful energy and burns her hand. She staggers to the bathroom, releasing it in the sink and notices her sister's bloody body in the bathtub and brother's head jammed in the window. She washes the blood off her hands only to have the medicine cabinet door swing open and knock her unconscious. When the water hits the mirror shard it explodes and the spirit is apparently gone.When Lacey tells Dr. Warren about her visit, he assures her that now that she has smashed the mirror she has rid herself of the ghosts from the past. However, in the barn, Willy picks up a paper bag filled with mirror fragments and lets its contents fall to the ground. The energy from the fragments disturbs the reception on his radio. While his back is turned, the invisible evil spirit approaches with a pitchfork but Lacey appears and pushes Willy out of the way before he is hurt. Willy takes a pale of water and throws it over the mirror fragments, which burn. (It is revealed here to the viewers that water is the only way of stopping the evil spirit.)Jake suggests that Lacey take their son, Kevin (Raymond Boyton), fishing to calm her nerves. As mother and son leave, a shard from the haunted kitchen mirror pops off and attaches to the sole of Kevin's shoe. At the lake, the reflection from the shard causes the spirit to impale one picnicker in the throat with a barbecue skewer while in his car. When his girl friend climbs into the front seat, the spirit pushes her so that she is also impaled by the skewer.At the farm, Jake picks up a shard of mirror on the kitchen floor and can barely place it back in the mirror because of its energy. However, it is enough to convince Jake that Lacey released the lover's spirit when she broke the mirror. The family summons Father Reilly to the house, and as the priest places his hand on the kitchen mirror, it glows red and the lights in the room go out. When a scream is heard from the barn, Jake and Father Reilly investigate and find Uncle Ernest pinned to the ceiling with a pitchfork, and Aunt Helen strangled with a garden hose.Back at the house, Jake tries to call the sheriff, but the spirit cuts the phone line. Jake taps Lacey's shoulder to get her attention as she fixes dinner, and she spins around, wearing a shard of mirror on her eye like a monocle. As she snarls, "get away," the shard's reflection burns Jake's face. Afterward, Lacey is about to attack Willy, but Father Reilly holds up a crucifix, and the evil spirit uses several kitchen knifes to attack Fathe Reilly. As blood pours from his head, the priest dislodges the evil shard from Lacey's eye. Father Reilly collapses and disposes of the mirror shard in the kitchen sink filled with water and the shard burs. Willy (speaking for the first time) screams out "Lacey!"The evil mirror's spell over Lacey is broken, but with the evil spirit still haunting the mirror, and Jake and Willy cover it with a tablecloth and dispose of it down the well, which the water makes the mirror explode.Some time later, Lacey, Willy and Kevin visit Helen's grave, expressing relief that the farm has been sold and that they can leave it behind. Kevin jumps up and down to show his excitement and dislodges the single surviving mirror shard from the sole of his shoe. As Lacey, Willy and Kevin leave the cemetery, the shard glows red unnoticed in the grass...