Forgotten (2017)

After moving into a new home, Yu-seok is brutally kidnapped by mysterious assailants. After he disappears, Jin-seok, Yu-seok's younger brother who suffers from nervous breakdowns, begins to have hallucinations every night. Miraculously, Yu-seok returns 19 days after his disappearance, and tells his family that he lost all of his memory due to shock. Jin-seok was glad to have his older brother back at first, but grows suspicious of him as he feels that something has changed ever since he returned. Jin-seok follows Yu-seok to see where he disappears to every night and faces a shocking truth.