Lights Out (2016)

During closing hours at a textile factory, an employee named Esther says goodbye to her boss, Paul. On her way out, she encounters the silhouette of a strange woman with claw-like hands. The figure disappears when the lights are turned on and reappears when they are turned off. After Esther leaves, Paul encounters the woman as well. He attempts to escape and locks himself inside an office, but the woman kills him after the lights go out.

Some time later, Paul's son, Martin, witnesses his mother, Sophie, talking to something in the dark. Sophie notices him and comforts him, but as he returns to bed, Martin sees a strange figure lurking in the shadows behind her. Terrified, he locks himself in his bedroom. Shortly afterward, Martin begins struggling to stay awake at school. When the school nurse cannot reach Sophie, Rebecca, Sophie's daughter from a previous relationship and Martin's half-sister, is called to the nurse's office. A Child Protective Services agent questions Rebecca about Martin's living conditions, and she reveals that Sophie takes antidepressants.

Martin tells Rebecca that their mother has been talking to a woman named Diana. Rebecca assures him that Diana is not real, explaining that she also heard Sophie talking to the imaginary girl when she was a child. When she and Martin arrive at Sophie's house, Rebecca argues with her mother after discovering that Sophie has stopped taking her medication. Sophie insists that Rebecca has no right to lecture her and accuses her of abandoning her, just as Rebecca's father did. Doubting her mother's mental stability, Rebecca takes Martin to her apartment, leaving Sophie devastated. That night, Rebecca awakens to find the same shadowy woman who killed Paul. She narrowly escapes an attack by turning on the lights, causing the woman to disappear. The following morning, Rebecca discovers that the name "Diana" has been scratched into her floor alongside a drawing of a stick figure. Recognizing the same name and drawing from her childhood, she realizes that Diana is real.

Rebecca searches Paul's office and discovers medical records and research revealing that Sophie was admitted to a mental hospital as a child. There, she befriended Diana, a young patient with a severe skin condition that prevented her from being exposed to sunlight. Diana was believed to possess the ability to influence people's minds, and her father had died by suicide after allegedly being manipulated by her. Eventually, hospital staff attempted to treat Diana using an experimental procedure involving intense light, accidentally reducing her to ashes. Meanwhile, a CPS agent takes Martin back to Sophie. Sophie speaks with her son and decides to let him meet Diana by turning off the lights. Frightened by the apparition, Martin flees to Rebecca's apartment.

Rebecca, her boyfriend Bret, and Martin stage an intervention to confront Sophie about Diana's influence over the family. Although Sophie becomes angry, she secretly begs Rebecca for help, admitting that Diana will not let her go. The group decides to stay overnight at Sophie's house, planning to seek professional help the following morning. To protect themselves, they illuminate the house as brightly as possible. However, Diana cuts the power throughout the neighborhood, rendering their precautions useless. She traps Rebecca and Martin in the basement and attacks Bret. Despite his injuries, Bret escapes by using his car's headlights to keep Diana at bay before driving away. Later, Sophie confronts Diana and begs her to spare her children, but Diana knocks her unconscious when she attempts to take her medication. In the basement, Rebecca and Martin find a blacklight that allows Rebecca to see Diana clearly, although its illumination proves insufficient to repel her.

Bret returns with two police officers. After freeing Rebecca and Martin, the officers spot Diana's shadow and pursue her, but she kills them. Rebecca and Martin escape the house, but Martin insists that they cannot leave Sophie behind. Rebecca returns alone to rescue her mother. As Rebecca climbs the stairs, Diana reveals that she killed Rebecca's father years earlier because he, like Paul, tried to help Sophie recover from her trauma. Diana attacks Rebecca for attempting to do the same and prepares to kill her. However, Sophie regains consciousness, takes a gun from one of the dead officers, and shoots at Diana. When the bullets have no effect, Sophie realizes that she is the link allowing Diana to exist in the real world. Determined to save her children, Sophie turns the gun on herself and dies by suicide, causing Diana to vanish.

After the terrifying night, Bret comforts Rebecca and Martin in an ambulance outside the house. When a light inside the ambulance flickers, the siblings grow uneasy, but Bret reassures them that Diana is truly gone.