Unlike many other films, which are disturbing either by dint of their naked unpleasantness (Man Bites Dog) or their sheer violence (most Peckinpah films), Deliverance shocks by its plausibility. Certainly, the buggery scene is pretty straightforward in its unpleasantness, but the film's effect derives far more from its slow build-up and the tangible sense of isolation surrounding the four leads, both before and after everything starts to go wrong. The moment when the canoes pass under the child on the bridge, who does not even acknowledge the men he had earlier played music with, let alone show any sign of human affection towards them, is among the most sinister in modern film. The tension increases steadily throughout the canoe trip, and perseveres even after the final credits - the ending makes the significance of the characters' ordeals horrifically real. The movie's plausibility is greatly aided by the playing of the leads, particularly Ned Beatty and Jon Voight as the victim and reluctant hero respectively. Burt Reynolds, too, has never been better. The film's cultural influence is demonstrable by the number of people who will understand a reference to 'banjo territory' - perhaps only Get Carter has done such an effective hatchet-job on a region's tourist industry. I can think of only a handful of movies which put me into such a serious depression after they had finished - the oppressive atmosphere of Se7en is the best comparison I can think of. Although so much of it is excellent of itself, Deliverance is a classic above all because there are no adequate points of comparison with it - it is unique.