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…

Ryung officially becomes a member of the Wangsoori Subway Police and Ji Seok’s partner. Ryung gets into trouble from the start, because she sneaks into the tunnels. Meanwhile, an elderly man who deliv…

Ryung and Ji Seok attend the disciplinary committee hearing and return to the station for night duty. Thanks to Ji Seok’s martial arts demonstration and a pot of noodles, Ryung gets her hands on the s…

Ryung and Ji Seok save Choi Do Chul just in time. Throughout their investigation, Ji Seok miraculously learns to appreciate Ryung’s over-the-top nature. Meanwhile, a star professional fighter becomes …

Ji Seok makes up his mind to kick Ryung out of the Subway Police for taking investigations into her own hands all the time. However, Ryung is attacked while out on an investigation by herself and ther…

A rumor circulates about people disappearing after they party all night on Club Day, then taking the first train home. Ryung and Ji Seok get on the first train to find out whether the rumor is true. D…

Subway Police and the Metropolitan Detective Division come together for a joint investigation. Despite Ji Seok’s jealousy, the joint investigation team switch partners. Ji Seok and Ma Ri become one te…

Ma Ri leaves Ryung after saying harsh words that keep replaying in Ryung’s mind. Still, Ryung continues her search for the Subway Ghost. But this time, she comes across someone willing to help. Meanwh…

Ryung and Ji Seok work together to save Jung Hoon and catch the kidnapper. With their great partnership, they discover the identity of the person who helps the kidnapper hide from the police. Meanwhil…

The Subway Ghost’s hideout is finally uncovered. Through the evidence found in the hideout, the police slowly start to piece together the Subway Ghost’s identity. Meanwhile, Ryung’s illegal investigat…

The police make headway on the Subway Serial Murders and narrow down the suspect list. After getting a tip about the identity of one of the Grasshoppers, Ryung and the Metropolitan Detective Division …

One of the Grasshoppers gets away from the police. The other two Grasshoppers confess that they only know him as Han Tae Woong, although that name turns out to be a fake identity. The investigation re…

Ji Seok and Ryung catch the remaining Grasshopper who everyone believes is the Subway Ghost. However, while being interrogated, the Captain of the Grasshoppers makes a shocking statement. The truth ab…

The police believe the Subway Ghost is in a mental hospital and that he plans to commit another murder. They chase him down and search the entire hospital building. Amid the chaos, Ji Seok’s mom and h…

Ryung and Ji Seok make their way into Kyung Hee’s house and find a room that looks like a young girl’s. After sharing the new evidence with Ma Ri and her team, they split up into two groups to chase b…

Finally, Ryung and the Subway Ghost come face to face. As his rage explodes, the Subway Ghost attacks Ryung, but another tragedy puts a stop to his actions in the end. Meanwhile, Jin appears at the sc…