"That single thought is enough. The impulse increases to a wish, the wish to a desire, the desire to an uncontrollable longing, and the longing (to the deep regret and mortification of the speaker, and in defiance of all consequences) is indulged."
Here, the narrator describes the process of committing a perverse action, from the first inclination to the implementation of the desire. At this point in the story, we are unaware that the narrator is talking about his act of murder here, which makes it a disturbing passage.
"Had I not been thus prolix, you might either have misunderstood me altogether, or, with the rabble, have fancied me mad. As it is, you will easily perceive that I am one of the many uncounted victims of the Imp of the Perverse."
The narrator says this after he reveals he is in prison for murder. He states that he did not tell us this earlier, as he did not want us to think he was mad. Following this, he suggests that he is not mad, but is instead "one of the many uncounted victims of the Imp of the Perverse", which doesn't do much to support his argument.
"The next morning he was discovered dead in his bed, and the Coroner's verdict was - "Death by the visitation of God."
After describing how he committed the murder, the narrator then states that he was not detected. He knew this for certain when the coroner pronounced that the death was not suspicious.
