If you believe Hammer Films' cornball exorcist caper is really "based on actual events", then you'll probably swallow anything. You'll believe that little plastic dolls can throw grown women to the sky, that cumbersome 1970s cameras were ideally suited for chasing poltergeists up stairwells, and that a bunch of flyweight young graduates are fit to share top billing with the splendid Jared Harris. The Quiet Ones, I'll concede, provides some shonky, retro thrills. But it's a joy buzzer in a joke shop or a pair of cut-price x-ray specs. Not convinced; not buying.