FORGOTTEN (2017) a.k.a Night of Memory and also Recall The Night .... no trailer because it's best to come to this knowing very little.
Jin-seok, 21-year-old, moves into a new house with his family. One night, his beloved brother is kidnapped before his eyes. After long silence of 19 days, suddenly Yu-seok returns home. And soon Jin-seok feels Yu-seok is a total stranger. Imdb
The first 45/55 mins of this Korean crime/thriller/mystery moves along ok as the initial plot developes then there is a big WTF? moment and things get tense and engrossing but the plot has still not finished messing with your head. A slick, intriguing, well directed gripping movie - atmospheric sound design too.