Plot
A security guard runs through a subway station until he enters a room he cannot escape and starts begging his reflection in a mirror for his life. His reflection uses a shard of glass to slice into its own throat; the wound reflects upon the real security guard's body, killing him.
Ben Carson, a suspended police detective, begins his first day as a night security guard at the Mayflower, a luxury department store gutted by a fire and shuttered five years prior. The building still contains numerous mirrors from the store.
On Ben's first night of patrol, he finds a mirror that appears covered with handprints, but only on the reflected side of the glass. He sees an open door in the reflection while it is actually closed. Over time, Ben begins to see more intense visions, which he initially shrugs off as hallucinations. He soon finds the wallet of Gary Lewis, the previous night guard (from the beginning of the film) who supposedly killed himself. Inside is a note that says "Esseker". After noticing the absence of blood on the mirror shard in Gary's crime photos, Ben is convinced that the mirrors make people do things to themselves that they are not actually doing.
Meanwhile, Ben's sister, Angie, is killed by her reflection as it grips its jaw and slowly pulls its mouth apart, causing her to bleed profusely. Ben is distraught when he finds her body. In anger, he attempts to destroy the mirrors at the Mayflower, but they are impervious to damage. He demands to know what the mirrors want, and cracks appear on one of the mirrors, spelling out the word "ESSEKER".
Ben begins searching for any information on anyone named Esseker in the newspaper articles that Gary Lewis sent him and his contacts in the police force. Failing to do so, he instead searches for Terrence Berry, the security guard who started the fire at the Mayflower 5 years prior. Learning Terrence has already died, Ben goes to the mental institute where he was incarcerated prior to his death, and is shown a video by Berry's doctor that was used in Terrence's trial where he blames the mirrors for his family's death after he failed to find Esseker.
Realizing his family is in danger, Ben races home and begins removing all the mirrors in the house. The family nanny, Rosa, concerned over Ben's behaviour warns Amy, who comes home to find Ben painting over the mirrors he cannot remove. Threatening to call the police - which will ensure that Ben will not be able to see his kids again, Ben takes Amy outside and shoots a mirror to show her they cannot be damaged. However, he is surprised when they do not repair themselves, and upon seeing his kid's faces terrified at his actions, Ben leaves.
Ben enters the flooded basement of the Mayflower and finds a small sign stating "Psychiatric Studies" and "St. Matthew's Hospital" underneath. He moves to the site of the leak and begins pulling at the tiles and brick of the wall and finds a room with a chair surrounded by mirrors beyond it, a Psychomanteum. Realizing that the Mayflower was built on the site of an earlier hospital, Ben asks his police friend Larry Byrne to help him locate the patient-employee manifest for the hospital. Larry finds the name Anna Esseker, a patient of the psychiatric hospital. She was twelve years old at the time and died in a mass suicide.
Ben looks through Anna's file and finds an Authorization and Consent form that negated her Death Certificate, stating that she had been discharged from the hospital two days before the suicide and is led to believe that Anna is still alive. Meanwhile, Ben's wife Amy discovers her son Michael's reflection acting differently from the real Michael. In a panic, she calls Ben, who immediately returns home. Together they cover every reflective surface in the house with green paint. They also cover the windows with newspaper and remove anything with a reflection, e.g. picture frames.
Ben locates Anna Esseker's childhood home, and discovers that as a child she was violent and uncontrollable, and diagnosed with severe schizophrenia. She was taken in by a doctor, Dr. Kane from St. Matthew's Hospital, who believed that she had a rare personality disorder. His treatment was to confine Anna to a chair surrounded by mirrors, believing this would cure her disorder by forcing her to confront her own reflection. Ben is told by Anna's brother Robert that when she returned, apparently cured, strange things started to happen with the mirrors in their home. As a result, her family sent her to a convent, Saint Augustine's Monastery, where mirrors are forbidden.
Ben visits the convent and finds Anna alive and well, who explains that she was actually possessed by a demon, which was drawn from her and became trapped in the mirrors. She explains that it collects the souls of those it kills and if she were to return, it would make it possible for the demon to be brought back into the mortal world. She refuses to go back.
Meanwhile, Amy discovers that Mikey is missing at home, and a thin reflective layer of water is completely covering the floor. After putting her daughter Daisy in a safe closet, she finds Michael using a knife to scrape the paint from the mirrors. Amy tries to stop him, but he escapes, obviously possessed.
Having threatened her at gunpoint, Ben returns with Anna to the Mayflower and straps her into the chair in the Psychomanteum. Back at Ben's house Michael is suddenly pulled through the water on the floor by his reflection and begins to drown. At the Psychomanteum the lights begin to flicker and the building begins to shake as the demons in the mirrors are released. They repossess Anna and all the mirrors in the Mayflower explode. Simultaneously, Michael is released from the demon's grip and Amy is able to pull him to safety. The repossessed Anna then attacks Ben, who manages to kill her by igniting a nearby gas line, setting off a huge explosion. The old building starts to collapse violently, and Ben is trapped under the ceiling while trying to escape.
Ben pulls himself out of the rubble and stumbles out of the building. Policemen and firemen are everywhere in the street, and a body is seen being taken in a bag by paramedics, but nobody notices Ben. He looks at the older security guard's name tag and sees it is written backward, realizing everything is in reverse (like in a mirror). He comes upon a mirrored surface in the city and fails to see his own reflection as he reaches out to touch it. He realizes that he died in the rubble and is trapped in the mirror world: his hand appears as a handprint on the glass surface in the living world.
