The narrator lives in a house with an old man, he loves the old man, and the old man has never insulted him; but there's one thing that keeps irritating the narrator.
It's the old man's vulture eye—a pale blue eye, with a film over it. It annoys the narrator enormously, so he makes up his mind to kill the old man, and rids himself of the eye forever!
The narrator starts cautiously creeping into the old man's room every midnight; trying to see the old man's vulture eye through the week ray from the lantern and seeking a chance to kill the old man—but the eye was closed.
It's the beating of his hideous heart!
Finally, on the eighth night, the old man notices the narrator's "visiting". Under the dim light, the vulture eye is open. As the narrator's heart beating getting louder, he drags the old man to the floor, pulled the heavy bed over him, and buries his body under the floor.
Because of the shriek last night, police officers come. The narrator welcomes them, convinces them, and tries to cover the truth up.
But a low, dull, quick sound starts echoing in the narrator's mind—it's the heart beating; as the sound grows louder and louder, the narrator's face becomes more and more pale. At last, he freaks out, and shrieks the truth.