Sunho falls off the school building. Sunho's parents are devastated to see their boy unconscious in the hospital. Meanwhile, Sunho's friends secretly delete a video playing the "Avengers Game" on their phones before meeting with the detective on Sunho's case.

The police concluded that Sunho made a suicidal attempt, but Moojin believes that Sunho would never make such choice and decides to find evidence by himself. He looks into Sunho's call records and notices that he called the same number repeatedly on the day of the accident. Meanwhie, Inha finds a button fallen off from Sunho's school uniform and finds it odd.