The Subway Police of Wangsoori Station is led by Chief Inspector Ko Ji Seok. He is the best of the best, although his only goal in life is to have a stable, uneventful career. However, a serial killer, nicknamed "the Subway Ghost", strikes the Subway Police 30 Year Anniversary event. An applicant shows up for a job interview to join the team.

The hard working, kind and timid Kim Mi Young (Jang Nara) has little in the way of education, beauty or wealth, but all that changes after a fateful night of accidental passion with the spoiled, rich heir of a family company, Lee Gun (Jang Hyuk). Her insignificant existence completely transforms when she finds out she is pregnant and must tie her life to his in a shot-gun wedding. The couple decides to make the best of a bad situation, but just when Lee Gun begins to show his growing affection for Kim Mi Young, his first love re-enters the picture to stake her claim.

As a reference to Article 38 which pertains to tax payments, this special police unit utilizes the criminals' own tactics of scams and deceit to catch rich tax cheats.