The Quiet Ones (2014)

In 1974, a student attends the class of Oxford University’s Professor Joseph Coupland, who wishes to prove that the supernatural does not exist. Coupland shows a video of a possessed boy and explains that research will be done to find a cure for this kind of disorder. One of his students, Brian McNeil, is invited to film the experiment process and joins Coupland, his two assistants Krissi Dalton and Harry Abrams, and their subject Jane Harper, a young woman who generates strange phenomena and has been abandoned. Jane is generally kept locked in a room with loud rock music playing during the daytime to prevent her from sleeping in the hopes that the regimen of sleep deprivation will result in increased activity.

Once his funding is taken away by an exasperated College Board that is both annoyed about the disturbances he makes and his lack of results, Coupland and his assistants settle in an isolated house in the countryside to keep experimenting on Jane. Her negative energy takes the form of "Evey", an infant doll-like creature that only Jane sees. Coupland instructs Jane to transfer her negative energy into a physical doll so they can destroy it. The further the researchers drive Jane to insanity with their methods, the stranger things get around the house. Brian is upset by the way Jane is treated and the lack of ethics in the experiment. Evey's apparitions become increasingly aggressive, and Jane begins to harm herself. There are also indicators that any attempt to harm Evey harms Jane.

Coupland refuses to stop the inhumane experimentation. He is irrevocably convinced that "Evey" is merely a conventionally treatable, psychological disorder in Jane's head, but the others become convinced over time that Evey is a real, malevolent, supernatural force. Brian and Jane become closer and share a kiss. When the group experience another attack by Evey, Brian goes to Oxford, where he discovers that a symbol that was marked into Jane is from a cult who worshiped a Sumerian demon. They performed experiments on a young girl a few years ago; their leader believed that Evey Dwyer, a girl with clairvoyant abilities, was the one to bring their "idol" into the physical world. Everybody in the cult died in a house fire that Evey set, including Evey herself. Brian returns and tells them about the cult, certain that Evey is a demonic presence who is possessing Jane. He convinces Harry and Krissi, but Coupland denies his theory and responds that Evey must be a figment from Jane's past rather than a demonic force.

Later that night, the group learns that the boy from the earlier experiments footage was Coupland's own son. After a heated argument, they are all marked with the same symbol Jane has. An unknown force murders Krissi and Harry. Jane realizes that she was the little girl that supposedly died in the house fire; she was born with clairvoyant powers and had set the house on fire to kill everyone. The authorities changed her name to Jane to give her a normal life, which is why negative energy is manifesting; Evey is not a demon, she is Jane's real identity (one who can't escape the trauma of her past life). Evey then attacks Brian, only for them both to be knocked out by Coupland. When Brian wakes up, he sees Coupland give Jane a lethal injection, as he thinks stopping her heart long enough for the negative energy to dissipate will permanently cure her. However, before Coupland can prove his theory, Brian subdues Coupland and brings Jane back to life. Once revived, Jane locks him out of the room and commits suicide by setting herself on fire.

The screen cuts to film footage, apparently from several months later, showing Brian sitting in a chair and holding a camera. An unseen speaker asks him about the deaths, to which Brian replies that everything was captured on film. The speaker replies that there is nothing on the film, and that everything in the house, including the films, were destroyed by the fire. When the speaker asks if Brian is responsible, Brian laughs maniacally and his hand starts to smoke, just as Jane's did.