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.
<span>The central message of the poem, then, is quite a simple one, but it is dressed up in the memorable guise of a vivid supernatural tale which has helped to ensure its popularity to this day. Its a</span><span> moral message, warning against thoughtless and foolhardy actions such as the one the Mariner performs in shooting the albatross. The albatross had done the Mariner no harm at all; in fact it seems it had helped to guide his ship, so that his wanton killing of it appears even more inexcusable.</span>