A brief moment that determined the vastly different destinies, fortunes and identities of two sisters from Yunnan on the China-Myanmar border is at the heart of “The Unseen Sister,” a mix of crime suspense and family drama that takes time to warm up before coming home strongly in the second half. Adapted from elements of Zhang Yueran’s 2017 novella, “Sister” is the most commercial film yet by leading Taiwanese filmmaker Midi Z. After opening with a bang domestically on Oct. 26, “Sister” launched internationally in competition at the Tokyo Film Festival.

As with much of Midi Z’s work, his latest film touches on aspects of his personal background. Of Chinese descent and born in Myanmar, Midi Z moved to Taiwan as a teenager and became a Taiwanese citizen. Interestingly, several of his credits on the end roll appear as “Midi Z,.” Though most of “Sister” takes place in Beijing, the...