The first thing a time travel story has to establish are the rules. Maybe the space-time continuum acts like Back to the Future, where one wrong move in the past could completely rewrite the present to the point where people fade from existence. Maybe it’s more like Harry Potter, where the relevant time travel has to happen to make events flow smoothly, meaning nothing from the past can really be changed. Or maybe it’s like Doctor Who, which has it both ways depending on what the story calls for.
