The Narrator hates the old man, because of his eye.
he watches the old man every night and plots his death because of his eye, his eyes bothers him!
Villains! Dissemble no more! I admit the deed! Tear up the planks! Here, here! It is the beating of his hideous heart!!
On the eighth night, he decides to get sneaky, to see the old man up close and personal. He decides to attack! He flips the bed over and suffocates the old man.
The police arrive to his house after someone called in a noise complaint. The officers check the house for anything but didn't find the old man, he hid his body well. The police stayed and asked him more questions
He begins to hear the steady heartbeat of the old man. Within his mind, he goes insane, he confesses to the police about the old mans body he hid under some planks.