In "The Fall of the House of Usher," why does the narrator go to the house?

The narrator of the story, is going to the house of his childhood friend, Roderick Usher. It has been years since he has seen Usher. Roderick has sent his friend a letter telling him that he has acute body illness of a mental disorder, which is oppressed him. The first lines of the story, set us up for the suspense that follows.

"During the whole of a dull, dark and soundless day in the autumn of the year, when the clouds hung oppressively low in the heavens, I had been passing alone on horseback, through a singularly dreary tract of country: and at length found myself, as the shadows of the evening drew on, within view of the melancholy House of Usher."

The narrator has come to see if there is any help he can do for Usher. He finds that Usher's twin sister, Madeline, is ill, as well. Usher tells his friend that his sister has died, and they need to put her in the family tombs beneath the house. The two men lay her body in the tomb, and the narrator tried to help his friend. He reads to him, and they both hear strange noises. Usher tells his friend that the houses is alive. The narrator thinks this is just his illness talking. The narrator soon finds out the real nature of the house.

This story is the typical Gothic haunted house story, which is so great. Edgar Allan Poe was a true genius at writing stories that stay with us longer after we are done.