Why does Roderick temporarily keep Madeline's body in the house after her death in "The Fall of the House of Usher"?
There are a few possible answers as to why Roderick Usher keeps the body of his presumably dead sister Madeline in the house after her death.
The first and most obvious reason would be the nature of Madeline's medical condition. In the story, the narrator says,
The brother had been led to his resolution (so he told me) by consideration of the unusual character of the malady of the deceased, of certain obtrusive and eager inquiries on the part of her medical men, and of the remote and exposed situation of the burial-ground of the family. I will not deny that when I called to mind the sinister countenance of the person whom I met upon the stair case, on the day of my arrival at the house, I had no desire to oppose what I regarded as at best but a harmless, and by no means an unnatural, precaution.
This paragraph gives us a few reasons for Roderick's decision, chief among them "the unusual character of the malady of the deceased." Madeline's illness can make her appear to be dead when she is still alive. Therefore, it is important, now that Madeline is supposedly dead, that he be sure she is actually so before turning her body over to someone else. Roderick also feels the "medical men" are too "eager," so he does not want to turn the body over to them yet. Finally, the setting of the family cemetery makes Roderick hesitate to have his sister entombed right away.
Another interpretation of Roderick's behavior comes to light at the end of the story, when Madeline is revealed to actually still be alive. It is possible that Roderick puts Madeline down in the temporary tomb below the house knowing she is still alive and, to some extent, orchestrating and anticipating the horrific closing scene, wherein he and Madeline die together, in each other's arms, as the house crumbles around them. We know that Roderick feels he cannot continue in life without his sister, so dying along with her is much more fitting.
According to Roderick, he feared that the medical men "would disturb her body" so he talked the narrator into helping him place her in a coffin and then put her in a vault until they later took her to the cemetery.
However, some believe that Roderick knew what he was doing when he buried her alive. Her skin was rosy enough that the reader could tell that she still had some life in her yet. The two of them had been cursed since birth, from their incestuous relationship, and this was his way of ridding himself of the curse.
Others yet believe that the narrator is also in on the burying her alive deal, and is just as evil as Roderick. Whichever plot seems correct, it all comes down to the fact that Roderick is sick. He is mentally sick, which affects him physically, and he either doesn't know what to do with her, or he intentionally wants to get rid of her. These actions of his just add to the horror of the story, which, after all is what Poe is all about in his stories.
Quite simply, Roderick decides to temporarily entomb Madeline within the house walls because he is afraid of his sister's body being stolen. The way Roderick describes this to the narrator, however, is quite cryptic. Because of the "unusual character of the malady of the deceased" there were "certain obstrusive and eager inquiries on the part of her medical men, and of the remote and exposed situation of the burial ground of the family." In other words, Roderick had the idea that this medical team who was attending to Madeline was very interested in her corpse for scientific purposes. They were even bold enough to find out that the Usher family burial ground was remote enough (whereas they could exhume the body unnoticed). The narrator also admits that the one member of the medical team encountered by his person had a "sinister countenance." Therefore, the narrator doesn't think this idea of the temporary entombment to be an "unnatural precaution."
Another interpretation explains Roderick's not allowing the medical men to touch Madeline as she, being cataleptic, may not truly be dead. In such a cataleptic attack, Madeline could be stiff as a corpse, leading the doctors to believe her dead and send her body to medical studnts for study even though she is yet alive.
In accord with troutmiller, this ambiguity is part of Poe's "arabesque" technique which embellishes the horror.