Time travel stories are always difficult because of the mind-bending conundrums they create. If time is linear and there is no multiverse, then time travel has the high probability of really fucking things up. If there is a multiverse and you can travel to them, how do you even know which one to get to?

Or, perhaps, there's nothing but me, and everything is but a figment of my over-active imagination. Nothing else is real.

(My 12 year old actually asked me that last week; how do I know that anything else is real other than me? It's a deep question).