Just, time travel is so very fascinating on this show! John sends Kyle back, and so Derek goes back as well! John sends Cameron back, past John grows too attached to Cameron so Jesse jumps back! Jesse comes from a future where Derek has theoretically already influenced the past and finds Fischer! SO MANY CIRCLES. You just don't know where to start and it's all mindbendy and wonderful and nothing ever gets fixed the way they want it to. I love it.