I have changed my first idea a bit, because it doesn't make sense that someone would lock themselves in a dark room for years then suddenly decide to escape. Also there isn't really any plot because I haven't decided on one yet. I need to think of a reason on why this man is living by himself in this room in the first place, aside from just paranoia. 
I've decided that he's committed a crime and is hiding from the police, but has only been in this room for about a week. The audience doesn't find out why he is hiding until later on in the film. There are police sirens in the background for a bit, and scenes of the crime keep flashing up. As he leaves the dark room/bunker that he's in he keeps looking back as if he's looking out for police or someone coming to get him. He keeps running and eventually collapses and the introduction blacks out.