Evil Within

Plot

Detective Sebastian Castellanos and his partners, Joseph Oda and Juli Kidman arrive at a crime scene located at the Beacon Memorial Hospital.

Having arrived, they find a massacre has taken place inside the hospital, with the place now seemingly deserted. After finding a sole survivor, Sebastian witnesses through the hospital CCTV, fellow K.C.P.D officers running from and firing upon an unseen force. They are then brutally killed by a disfigured, supernatural, hooded man, who then appears behind Sebastian and attacks him, knocking him unconscious. Sebastian then awakes in the basement of the Hospital, and is forced to flee flee from a monstrous man wielding a chainsaw.

Upon reuniting with his colleagues, they attempt to escape via ambulance while Krimson City is destroyed and rearranged by a massive earthquake, eventually causing them to crash. Freeing himself from the wreckage, Sebastian wanders through unnatural forests and abandoned buildings full of monstrous creatures, and witnesses the apparition of a disfigured man in a white hood. Trapped in the nightmare world, Sebastian encounters one of Beacon's doctors, Marcelo Jimenez, who is searching for his patient, Leslie Withers. Jimenez identifies the hooded stranger stalking them as Ruvik.

Sebastian eventually reunites with Joseph, though it is shortly revealed that Joseph is suffering from a strange form of transformation which compels him into a murderous rage. While he is able to control it for the most part, Joseph warns Sebastian to be wary of him if he turns. The two eventually find and rescue Kidman from drowning in a crude contraption, though they are soon separated again after hearing the high pitched noise.

Elsewhere, Kidman is being forced to relive memories of her indoctrination into an organization known as Mobius. It is revealed that Kidman is actually an undercover agent, sent by Mobius to retrieve Leslie from Jimenez, apparently as leverage to force Jimenez to continue working for them. Jimenez had been working with Mobius on a project known as STEM - a machine capable of uniting minds into one, with one influencing mind at its center. Jimenez activated STEM without Mobius' permission - signaled by the high-pitched noise - but Mobius anticipated this, and trained Kidman to navigate the STEM world and retrieve Leslie.

Sebastian learns of the story of Ruvik, born Ruben Victoriano, through various memories that Ruvik places him in. Ruben was an intellectually gifted but mentally unstable child, and was close to his sister, Laura. While playing in a barn on their family's estate, Laura was killed and Ruben severely burned after the barn was set on fire as an act of revenge against their parents. Ruben's father began hiding him in the basement of the family manor. Deeply traumatized over Laura's death, Ruben eventually killed both of his parents, took control of their fortune, and continued to "donate" money to Beacon Mental Hospital in exchange for test subjects for his experiments into the human psyche.

Ruvik began designing STEM as a means for him to reshape reality, so that he could physically travel back into his memories and live his life again with Laura. Jimenez then took notice of Ruvik's work, and revealed it to Mobius, who wished to use it for their own purposes. However, with the machine only being calibrated to work with Ruvik as its center, Mobius were forced to use Ruvik's brain after killing him, which allowed Ruvik to maintain control of the STEM world. Kidman realizes that Mobius in fact wants the meek Leslie as a replacement for Ruvik's brain - an easily manipulated 'blank slate' mind, which they can use to power STEM and create a world of their own design.

When Dr. Jimenez, aided by Sebastian, tries to use Leslie to return to reality, he realizes that Ruvik wants to transfer his mind to a compatible host, and escape into the real world. A beast created from Ruvik's subconscious then kills Jimenez, and Ruvik scatters the group across his mind. Kidman finds Leslie first, and is about to shoot him to prevent Ruvik from using him as a host, when Sebastian and Joseph intervene, prompting her to shoot Joseph, before Ruvik separates them again. Kidman tries desperately to turn against Mobius, but realizes that she has been given a serum which has allowed Mobius to travel into the STEM world with her.

Sebastian finds Leslie, and guides him back to the hospital. At the top of the lighthouse, he sees his own body in a bathtub hooked to the STEM machine. Kidman arrives and attempts to convince Sebastian that Leslie has to die. Ruvik interrupts them, gets hold of Leslie, and absorbs him.

Sebastian battles a gigantic creature created from Ruvik's subconscious and defeats it, waking up in the bathtub. He pulls himself off the machine, removes Ruvik's brain from the STEM, and crushes it. He wakes up in the tub again with Kidman by his side, monitoring him and Joseph, who is unconscious in a second tub next to him; Kidman motions for Sebastian to stay quiet. Sebastian falls unconscious, and later wakes up in the same tub, with no one around except for the bodies of Jimenez and Connelly. As police and S.W.A.T. reinforcements arrive, Sebastian exits the hospital and notices Leslie walking out of the main gates. Sebastian has a brief headache — a sign of Ruvik’s influence on subjects within the STEM — which causes him to lose sight of Leslie. It is implied that Ruvik has returned to the real world, and is able to influence those who were connected to his machine, intending to take revenge on the organization that betrayed him.