Is the climax of "The Tell-Tale Heart" when the narrator kills the old man, or when his deed is discovered?
The admission of guilt is generally considered the climax of "The Tell-Tale Heart." The story builds and builds to this point with the relentless beating of the heart after the man has died, until it has driven the narrator to confess his deed. This story is structured in a very focused and brief way, in which the climax takes place in the last paragraph. The climax and denouement are one and the same.
Hearing the old man's heartbeat beating unusually and dangerously quick from terror, the narrator decides to strike, jumping out with a loud yell giving the old man a heart attack and then smothering the old man with his own bed. The narrator proceeds to chop up the body and conceal the pieces under the floorboards. The narrator makes certain to hide all signs of the crime. Even so, the old man's scream during the night causes a neighbor to call the police.