I think that there was so much potential for this series. While I'm glad I watched it, there was so little depth. This fourth and final episode deals with time travel. Of course, the most fundamental issue with this topic is the impossibility of traveling back in time. Thee can be little doubt than any action will eventually mutate the future. This is well stated. We are given glimpses of "The Time Machine," "Back to the Future," "The Time Traveler's Wife," "Blade Runner,""Groundhog Day," "Quantum Leap," and too much "Dr. Who." It's obviously, the BBC, so things are just a bit skewed in their direction. I would love to see a science fiction history that doesn't categorize.