The descriptions of the Usher family home and of Roderick and Madeline create an atmosphere of evil and dread that pervades the narrative from the very beginning. The house itself is referred to as a "mansion of gloom" that seems to cast its shadow over its occupants, both Roderick and Madeline have a ghostly pallor, arousing feelings of unease in the narrator. Many renderings of the story have explicated the evil behind the curse Roderick speaks of as the outcome of a long history of incest and inbreeding in the Usher family. According to this interpretation, the brother and sister are suffering the physical and emotional consequences of the guilt linked with such commonly condemned behavior. Yet others see the evil and sense of foretelling in the story as something of a purely supernatural nature; this interpretation characterizes Roderick's behavior as a natural response to the transcendental forces that are haunting his home. Roderick speaks several times about the mysterious illnesses from which he and his sister suffer. His progressively unstable mental condition and ultimate emotional breakdown at the end of the story have led many to view "The Fall of the House of Usher" as an exploration of the themes of madness and insanity. Madeline's illness, a condition that causes extreme muscle rigidity and periods of unconsciousness, is quite possibly misunderstood or even purposely interpreted as death by her mentally unstable brother, whose irrationality steers the story.