The Mimic (2017)

Hee Yeon (played by Yeom Jung Ah)'s son Jun Seo was lost in Seoul. Heartbroken, she took her amnesiac mother-in-law back to her hometown of Changshan to recuperate, hoping that her mother-in-law would remember how Jun Seo disappeared soon. One day, Xi Lian met a ragged mysterious girl in a cave near Changshan Mountain. Perhaps she felt pity for her, or perhaps she was out of curiosity...