What is the tone/mood of "The Tell-Tale Heart"?

The overarching sense of anxiety and nervousness characterizes the tone and mood in the atmosphere of "The Tell-Tale Heart."  The narrator begins the story by trying to convince the reader that he is not mad, and later in the story, he continues to try to make the reader believe that he is sane.  The narrator is nervous that he in fact might be mad, and his anxiety causes him to behave in irrational ways--namely, by plotting to kill the old man.  Similarly, at the end of the story, the narrator puts on a show for the police officers by parading them around the house to show that nothing has gone amiss during the night.  But the narrator harbors anxiety over his crime, and his own nervous guilt causes him to eventually tear up the floor and give himself away to the police.