Complex sentence: "Part One" 's setting was altered after production learned of a pre-existing set previously used for the Western television series "Bordertown", and the choice of location in turn influenced the type of supernatural monster that was featured.
Split into simpler sentences: Part One 's setting was altered after production learned of a pre-existing set, which had been used for the western television series "Bordertown". The choice of location in turn influenced the type of supernatural monster that was featured.