Secret (2009)

Sung-ryeol is a detective in charge of violent crimes. He is an upright man, but is having an affair with his colleague's wife, and it is the reason he loses his own daughter in a car accident. Wracked with guilt but unable to explain to his wife, Ji-yeon, what happened on that day and why, he loses her in her grief. Ji-yeon comes home shaken and bloody late one evening, peaking Sung-ryeol's curiosity about his wife's behavior. The next day, Sung-ryeol finds trace evidence that points to his wife while investigating a murder scene. He presumes that his wife is connected to the case, and does all he can to keep her from being identified as a suspect. When an unidentified man shows up claiming to know Ji-yeon is involved and asking for money, the situation is made worse by Ji-yeon refusing to offer Sung-ryeol an explanation or tell him any kind of truth.