The Evil Within

In "The Evil Within," a mentally handicapped boy named Dennis lives with his older brother John, who is haunted by a sadistic creature that orders him to go on a murderous rampage. As Dennis's nightmares become more vivid, he begins to kill people he loves, and his reflection becomes more articulate, revealing a sinister purpose. Despite John's efforts to stop him, Dennis continues to kill, and the townspeople start to disappear. In the end, Dennis is taken away by the police, but the true horror is revealed when it becomes clear that the Cadaver has taken control of Dennis's mind and body, leaving him trapped in his own subconscious, unable to escape the carnival ride of terror.

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Some movies that have similar genres and were produced around the same time as The Evil Within include The Hospital, Lights Out, The Boy Behind The Door, The Sadness, X, Wrong Turn 6: Last Resort.