Who can you trust if you can't trust yourself?

Yoo-jin, an exemplary son and a swimming champion who has just applied to law school, wakes up early one morning to a strange metallic smell and a phone call from his brother, asking if everything is okay at home - unanswered by their mother in the wild night. Yoo-jin soon discovers her body, in a pool of blood at the base of the staircase in their duplex in Seoul. He doesn't remember much about the previous night; only his mother calling his name. But - was she calling him for help? Or begging him not to kill her? Thus begins Yoo-jin's desperate three-day search: he tries to unravel what happened that night, and finally learn the truth about himself and his family.