There were several reasons why Saki chose to have Framton Nuttel suffering from a nervous condition. In the first place, it helps to explain why this city dweller is spending time in the country. He needs to relax in a quiet, peaceful setting. This, of course, is ironic because he is going to be scared out of his wits. Secondly, the fact that Framton is suffering from a nervous condition makes him particularly susceptible to the practical joke that Vera plays on him. He is already jumpy, and it wouldn't take much to set him off. Thirdly, his nervous condition is a felicitous way for the author to characterize him; it makes it easy for the reader to visualize the unhappy stranger sitting on the edge of his chair, tugging at his collar, trying to pay attention to his young hostess, and so on. The main point of the story is not just that a man is frightened by what he thinks are approaching ghosts, but that a man who is seeking a rest cure for bad nerves runs into such a shocking experience in what should be, and actually is, a peaceful English country home where tea time is one of the most exciting events of the day. A fourth reason for Saki's making his main character a nervous hypochondriac was that it makes the story amusing rather than frightening. This is not a horror story but a humor story spiced with a bit of the uncanny, and as such is characteristic of much of Saki's short fiction.