Why is the story titled "The Tell-Tale Heart"?
The unnamed narrator lives with an old man who has a spookily cloudy eye. The narrator appears to be crazy. He puts up with the old man for a long time, but the eye drives him further and further over the edge of insanity. Finally, one day, he murders the old man and buries his body under the floorboards. When police come to investigate (neighbors had complained of strange sounds coming from the house), the narrator believes he hears the old man's heart thumping beneath the floor. It sounds so loud to him that he confesses, screaming at the police: ‘‘I admit the deed!—tear up the planks!—here, here!—it is the beating of his hideous heart!’’
It is called "The Tell-Tale Heart" because the heart, he believes, has betrayed him and told of the narrator's crime.