An Ally or a Foe?

Dong-joo 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.