Essays / How to convert a 3-point thesis statement into an idea. Essay on Short Story. [2]

Hi, I'm writing an English course essay on the short story "The Cask of Amontillado" by Edgar Allan Poe. The essay topic that I choose for the essay is "Does Montresor punish Fortunato with impunity?", I already have the essay done, but I have to change my thesis statement from a 3-point statement to an idea. The problem here is that I don't really know how to change it into an idea, since I have never really been taught that.

Thesis: The narrator and main character Montresor manages to succeed in punishing his secret enemy, Fortunato, with impunity by not having any sort of legal punishment placed upon himself, nor any feelings of guilt of his wrong doing and not having any misfortune happen to him during or long after his questionable, although justifiable to Montresor, revenge on Fortunato.

If you guys could help me out, or just give me some sort of direction, that would be great. Thank you.