Plot
A security guard runs through a subway station until he enters a room he cannot escape. He starts begging his reflection in a mirror for his life. His reflection cut its own throat with a glass shard; 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.
After several nights, Ben notices unusual and increasingly unsettling things about the mirrors. He soon finds the wallet of the previous night guard (who died in the beginning of the film) and a note that says "Esseker". Ben eventually comes to suspect that the mirror reflections make things happen to people.
Meanwhile, Ben's sister, Angie, is killed by her reflection as it slowly tears off its lower jaw, causing her to bleed to death. Distraught and angry by her death, 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".
Failing to find "Esseker," Ben searches for Terrence Berry, the security guard who started the fire at the Mayflower 5 years prior. He goes to the mental institute where Terrence was incarcerated prior to his death. In a video, Terrence blames the mirrors for his family's death after he failed to find Esseker.
Realizing his family is in danger, Ben races to his ex-wife's home and gets rid of the mirrors, painting over those he cannot. His ex-wife Amy, disturbed by his behavior, threatens to call the police - which will ensure that Ben will not see his kids again. Ben shoots a mirror in an attempt to prove to her they cannot be damaged. However, the mirror remains broken, and upon seeing his kids' terrified faces, Ben leaves.
Ben investigates the Mayflower's basement and uncovers a room with a chair surrounded by mirrors, a Psychomanteum. Realizing that the Mayflower was built on the site of an earlier hospital, Ben eventually finds out about Anna Esseker, a patient of the psychiatric hospital. She was 12 when she supposedly died in a mass suicide.
Finding a record of Anna being discharged from the hospital two days before the suicide, Ben is led to believe she is still alive. Meanwhile, Amy notices her son Michael's reflection acting differently from her real son. She calls Ben, who immediately returns home. Together they cover or remove everything with a reflective surface.
Visiting Anna Esseker's childhood home, Ben learns she was violent, uncontrollable, and diagnosed with severe schizophrenia. At St. Matthew's Hospital, Dr. Kane's treatment was to confine Anna to a chair surrounded by mirrors. Anna's brother Robert recalls 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.
At the convent, Ben finds Anna alive and well. Anna explains that she was possessed by a demon, which later became trapped in the mirrors. The demon collects the souls of those it kills. If she returns, the demon would be able to escape into the mortal world. She refuses to go back.
Meanwhile, Amy discovers that Mikey is missing, the floor is covered by water. Putting her daughter Daisy in a safe closet, she finds Michael scraping the paint from the mirrors. Amy tries to stop him, but he escapes, having been possessed.
Ben forcefully brings Anna to the Mayflower and straps her into the chair in the Psychomanteum. Michael is pulled through the water on the floor by his reflection and begins to drown. At the Mayflower all the mirrors explode as the demon repossesses Anna, sparing Michael. The possessed Anna attacks Ben, who manages to kill her by igniting a nearby gas line, setting off a huge explosion. The old building collapse violently, trapping Ben.
Ben pulls himself out of the rubble and stumbles out of the building. He sees policemen and firemen, and a body is brought out in a bag by paramedics, but nobody notices him. After noticing everything is reversed, Ben realizes he died in the rubble and is now trapped in the mirror world.
