In "the-tale heart" by edgar allan poe, what does the beating heart that the narrator hears symbolize ?

The person narrating has committed a murder and shoved the corpse under his floorboards. As some time passes the heart beat is a glimpse into his insanity, and how he is delusional over hearing non existent sounds. He believes he hears the heart of the person he murdered under the floorboards, which is a delusion, most likely made out of paranoia. When the police come to ask about the victim, the man almost fools them until he breaks down and confesses. He expressed annoyance at the victim earlier, saying that he could not get away from their eye, I believe. He tried to solve this by killing them, but his mind would not let him do so by making up false realities. 

Sample Response: In the Civil War era, spy work was done by amateurs without training or a professional network. Elizabeth Van Lew was one woman who started working as a spy for the Union because she believed slavery was wrong. Eventually her responsibilities as a spymaster grew to the point where she helped organize structures and systems that helped spies do their work.