The discovery of skeletal remains and a student card with Lee Ha-neul's name at Sopyung Lake marks a significant shift in the investigation. Kang San is heartbroken, fearing the loss of his brother. Meanwhile, Hye-kyung becomes suspicious of Tae-man's attention towards the boy living with Dong-ju. Acting as if she is unfamiliar with the boy, Hye-kyung accepts Kang San's picture from Tae-man but immediately visits Dong-ju's house, bringing a mysterious gift.

Dong-ju and Kang San stumble upon a flash drive inside a gift Hye-kyung left behind after her short visit. The data inside seems significant enough to shake the whole country. The two feel the need to be honest with each other if they are to work together toward the truth. Meanwhile at the station, the flash drive goes missing, and the last person who held on to it was Detective Kim. Kang San's pursuit of his brother continues.

The police investigation intensifies as they start suspecting Byun Jong-il's involvement in the Jeon Doo-hyun murder case. Simultaneously, No Myung-nam is discovered in an alleged suicide attempt. Meanwhile, Kang San confides all his secrets to Hyun-soo, who then seeks a favor from him. However, Dong-ju vehemently rejects the idea for Kang San's well-being. On a hospital bed, Myung-nam remains unconscious, and Kang San tries to read his troubled state of mind.