Horror films are always at their most viscerally frightening when they start with the commonplace. This is often no reflection on the quality of the filmmaking, just of the fact that it's relatively easy to avoid spending the winter in a snowbound hotel, or opening an orphanage. The films that make your heart race after you leave the cinema are the ones that follow you home - when you fall asleep, you watch a videotape, or, as in The Strangers, you're at home alone one night and there's a knock on the door. Kirsten (Liv Tyler) and James (Scott Speedman) are spending the night at his parents' summer house. A girl knocks on the door looking for her friend and then goes away again. James goes to buy cigarettes, and Kirsten hears strange noises and starts to suspect there is someone in the house. The director Bryan Bertino squeezes every possible drop of tension out of the genuinely terrifying first 20 minutes. The middle section, in which James and Kirsten try to escape from their three masked tormentors, is less impressive but still manages moments of breath-holding, face-covering suspense. But the final chapter is a return to form, as enigmatic and intriguing as one of Stephen King's best short stories. The Strangers is a mixed bag, but it's also a lesson in how to turn some of our most everyday fears into a brilliantly frightening film.