The character himself is insane, though he thinks the reader is insane for thinking that he is. He believes what he did was good until the police showed up, and he thought he could he the old man's heart, but it was his own (in other words his conscience got the better of him). The conflict is that the character went mad because of the old man's eye, he would sneak his head through the old man's door and watch him sleep, till one night he accidentally made a noise, which woke up the old man. When the character saw the man's eye, he snapped and killed the old man be suffocating him. The setting is where mostly in the Characters home, and in the Old man's room.
I hope i helped! To be honest its a really good story, you should read it!