When I read the plot I somehow knew that I know this. And when I started watching and I definitely could figure out what was happening.
The movie starts with Sang-woo waking up in a hospital after a near fatal car accident which has taken away his memory. He has no idea who he is and who his wife is. As the story progresses we see him getting confused with flashes of memory and texts from a private investigator whom he had hired before the accident to spy on his wife. To make the matters worse he soon finds out that his wife might have been cheating on him and has been hiding this from him.
The plot offers nothing new and you might guess where it is headed from the first few scenes itself. The acting too was not worth a mention and becomes irritating from time to time.
The final twist/reveal doesn't explain much about how things were handled and will leave you completely unsatisfied. To me it seemed that the director took too much time in building up the plot with non sense sub plots and yet rushed the end without providing proper explanations.
Gets a 4/10 from me. Save your 100 mins by avoiding this.