Am I the only one that thought he was...
Hallucinating?
Given that I hadn't read the synopsis (thanks IMDb for giving away that there's a supernatural element to it), I couldn't believe that Christopher Lloyd stabbed the guy in the blue jacket. I was half convinced Cleaver was hallucinating it. Then when he was in the psych office, he talked about the girl crossing the street, and she got hit by a car, but it was just his imagination. Ok, there was the barber shop scene, but...
So while I wasn't fully convinced, I was 50/50 throughout the film.