The ghost story is essentially a folk form, usually better told than written. We know this, having listened to so many ourselves - punctuated by the swatting of mosquitoes during power cuts, and in train journeys, after which the long blue-lit corridor to the toilet was impregnated with silent menace. At some time or other we have all shot that slightly shame-faced look over the shoulder after a hair-raising story-telling session. This oxymoronic spin - the pleasing terror, the delicious fright - is fundamental to our enjoyment of tales of the spectral. Paradoxically, the more terrified we are, the better the story.