Time travel is a popular sci-fi theme because it’s tempting to think that changing the past would improve the present. Even if time travel were possible—as it is in the k-drama sci-fi thriller Sisyphus: The Myth—fixing the past is not likely to be simple. In the JTBC drama Park Shin-hye plays the well-intentioned time traveler Kang Seo-hae. She lives in a hellish future that was reportedly set on course by the actions of a single man, Han Tae-seul, played by Cho Seung-woo. So, when Seo-hae arrives in the present, without shoes and carrying a mysterious suitcase, she wants to start looking for him and fix the future. Yet she’s…