The clumsy new team brings trouble to the Gangnam police station on their first day. When they are given a chance to prove themselves while undercover, things don't go as planned.
A seven-year-old boy is killed in a hit-and-run accident. The P4 search for clues to find the culprit. Team Leader Seo is reminded of a tragedy from his past.
The case of the dead father is solved. While working on their next assignment, Soo Sun learns Dae Gu's real identity. Using DNA testing, Pan Seok also confirms his suspicions.
Now that the man from Dae Gu's past has been arrested, the team tries to find his accomplice. A problem arises with Soo Sun's mother.