Every night, the narrator quietly goes to watch his roommate, an old man, who he loves, sleep. He is scared by his blue eye, which chills his blood when it looks at him.
He wants to find the old man when his blue eye is open because he wants to kill him.
The narrator kills the man. He drains all of his blood and pulls up the floorboards under the bed to hide him under them.
The police come to the door because a neighbor heard a scream. The narrator is confident that nobody will find out and is proud of how good he hid the evidence, so he brings the police into the room where he is buried so they can see that there isn't any evidence.
They are talking, and then the narrator begins to hear the old man's beating heart, even though he's dead. He is convinced that the policeb hear the heart too, but weren't saying anything and were taunting him. The narrator ends up confessing.
The narrator is not reliable. He had a disease, he can hear creepy things, and he decided to kill a man that he loved just because he was scared of his eye.