I just played the game recently, it is very good, and hard to win. Sirenhead will follow you if you have the flashlight on. If the sounds he makes are getting louder, you're getting to close! It can be hard to find all 5 phones, but once you do, head for the police car, because Sirenhead's right behind you! If it's too dark, adjust brightness, easier to see around w/o the flashlight.
How about making a difficult level, where Sirenhead chases you even w/o the flashlight.