A couple episodes ago, the show hit upon one of those tropes that all time travel shows must at some point deal with--what to do about the big evil from the past. Because anyone who has a passing acquaintance with The Twilight Zone knows that just going and killing the big evil won't work out the way you expect.
Which brings me to this week's question:
What if you ended up back in the past and you met up with some awful monster who you knew was going to do horrible things in his/her future? How could you neutralize that threat without making it happen anyway? Or would it be better to let their future/our past play out the way it did in the original history?