Secret Sunshine (2007) on Netflix

Plot summary

A traffic accident leaves Lee Shin-ae a widow, and she moves with her son Jun to Miryang, the town her husband came from, where she opens a piano academy. Kim Jong-chan, the mechanic who repairs her car on the way in, keeps helping her look at land for a house, saying he is just being a Good Samaritan. She meets a middle-school girl whose father teaches at Jun's daycare, and a pharmacist gives her scripture, saying faith in God is the answer to her troubles. Her brother visits from Seoul and asks why she settled in Miryang, claiming her husband had cheated on her; she denies it. One night she comes home late and Jun is missing.