Write a story in which a character is vulnerable and another characters senses this and takes advantage of the situation. However, do NOT make the 2nd character “evil”, give that character depth. “Bad people” (even criminals) don’t see themselves as bad. In fact, they sometimes think of themselves as ‘heroic’. For an example, here’s my story “Mating” in Jellyfish Review. This story is in the collection “Alligators At Night”.