Seoul city's metro police investigative squad meets its 30th anniversary and tasks to convict a petty thief. Yoo-ryung reads an advertisement for new recruits and applies to the squad. She is unsuccessful in application.

Yoo-ryung hears suspicious noise whilst on patrol, and enters an off-limit area. Captain Go Ji-seok,finds Yoo-ryung unconscious and warns her never to enter again.

The Seoul city metro investigative squad investigates a case of contract killing. The squad seeks evidence and witnesses.

Kim Won-tae is arrested for charges of assault and battery, and upon search of his history it is revealed an ex-girlfriend was murdered. His girlfriend declines the need for an apprehended violence order.

Captain Go and Yoo-ryung experiment with a rumor which states, on the last friday of every month, an all-night clubber disappears on the first train. Captain Go tails a petty thief.