Returning home from the rooftop party, Shi Mok discovers that an intruder has left something in his bedroom. Yeo Jin and Gun come over right away.

Yeo Jin suspects a new killer is involved in the latest murder incident. Meanwhile, Shi Mok collapses after leaving the autopsy.

Yeo Jin collects evidence as Shi Mok interrogates the suspect. Many questions get answered, but the most important problem of all remains to be solved.