Tae Hoon is seemingly doing homework when he gets a call.
Si Mun is recaps what they know about Hyo Won's supposed suicide, including a postmortem wound on his hand and the fact that the fence was broken in the act. He then wonders why Hyo Won would've jumped backwards if he committed suicide, but also why he would've hurt his hand in the process. Had he planned his death, it would've stood to reason that he brought tools to break open the fence. If his death wasn't planned, then it would've made more sense to just jump over the fence.
Then, remembering that Hyo Won mistook Si Mun for Tae Hoon, he conjects that perhaps he had done the same to the other students and that his prime targt, Tae Hoon, may have been responsible for his death. Tenka says that they need evidence, but Si Mun says that they already have a witness. Tae Hoon pushed hard to insist that Young Woo wasn't worth interviewing, and since he was at the crime scene, it stands to reson that he may know more than he's telling.
Young Woo is in his bedroom, skipping school for fearing Hyo Won's spirit and sending a video to Baram when he remebers the day Hyo Won died.
Hyo Won and Young Woo were together while Young Woo captured video of a puppy playing when they saw Tae Hoon and asked how his tests went. He ignored them and walked away.
Later, Hyo Won catches Tae Hoon vandalizing school property and confronts him, all the while Young Woo records a video of what he perceives as bullying on his cell phone. Tae Hoon claims that Hyo Won kept taking his chances away and tells him to leave him alone, so Hyo Won retalliates by punching him in the face. Tae Hoon hits back, slamming Hyo Won into the fence and causing the wound on his hand. He then tells Hyo Won to "just die" and Hyo Won slips through the fence.
Hanging onto the ledge, Hyo Won pleads for his friend's help, but Tae Hoon stomps on Hyo Won's hand causing him to fall to his death. He then notices Young Woo and coercing him into staying quiet.
The message to Baram sends, but Tae Hoon appears behind Young Woo and is both shocked and enraged to see that he'd recorded the entire event.