In "The Open Window," why is Framton Nuttel taking a trip?

Mr. Nuttel’s peculiar name is very descriptive of the “nervous condition” from which he suffers. He seems to have some sort of mental disorder that keeps him anxious and unable to handle stress. When he describes his illness, he says, "The doctors agree in ordering me complete rest, an absence of mental excitement, and avoidance of anything in the nature of violent physical exercise.” Mr. Nuttel’s sister suggests that he go to the country home of Mrs. Sappleton and soak in the fresh air to relax his nerves. Unfortunately, the “nerve cure” he has come to the country to receive is made worse by the pranks of fifteen-year-old Vera, who tells him a sad and eerie story about the death of her aunt’s husband and brothers while hunting. Mr. Nuttel is enthralled with the story when Mrs. Sappleton, Vera’s aunt, comes in the room to finally greet him. At that moment, Mr. Sappleton and the brothers walk home across the lawn from hunting. Mr. Nuttel truly goes “nuts," thinking he is seeing ghosts, and he leaves the estate scared and more nervous than ever.