Kate Bowman is a by-the-books social worker who is investigating a series of mysterious deaths. Each victim suffered from sleep paralysis, a frightening ailment that immobilizes its victims as they dream. Kate is approached by an unorthodox doctor who warns of an evil entity that haunts people in their sleep. She brushes aside his admonition, but when a terrifying entity begins to haunt Kate's friends and loved ones, she must fight to stay awake to stop the nightmare she's unleashed.