Matt Cullen is checked into rehab after witnessing a horrific death during a drugged-up party. Three months later, he is set to get his life back together, staying at his parents' mansion in the hills of Los Angeles. But things have changed around Matt and everything seems off balance. Fueled by his unstable personality and the invading power of social media, Matt’s paranoia grows, messing up with his rehabilitation program. As he starts using again, a mysterious presence starts growing around Matt, and a monster that has been haunting him since he was a teenager reveals itself. His therapist tries to help, convinced that the monster is actually in Matt’s head.