Gap dong

Plot

1996, the (fictional) city of Iltan in Gyeonggi Province: A young girl gets brutally murdered by an unknown person on a dark night. As the city is gripped by a succession of serial killings, a total of nine murders within a twelve-kilometer radius since 1993, the police conclude that a man they've nicknamed "Gap-dong" is behind the crimes. But detective Yang Cheol-gon is convinced that the actual killer is Ha Il-sik, a resident of the town who is intellectually challenged. His attempt to arrest the suspect fails as Ha commits suicide to prove his innocence. His death inspires his son Moo-yeom to become a cop to clear his father's name and restore his honor.

Seventeen years later, Moo-yeom is a police detective who spends his career chasing dead ends and helping juvenile delinquents. After the statute of limitations on the case expires, Moo-yeom becomes resigned to the belief that Gap-dong is dead. But then a series of incidents occur in the town that bear an eerie resemblance to Gap-dong's crimes. Cheol-gon, now a well-decorated officer, has recently transferred back to Iltan, and to his dismay, Moo-yeom joins his investigation team to catch Gap-dong once and for all.

Main characters

Yoon Sang-hyun as Ha Moo-yeom

A detective in Iltan Police Department's violent crimes unit. He vows to avenge his wrongly accused father.

Sung Dong-il as Yang Cheol-gon

He was a police inspector at the time of the original murders, and is now a well-decorated officer. Upon receiving his latest promotion, he surprises his superiors by requesting to be assigned back to Iltan, because he wants to end his career by capturing Gap-dong. Still convinced that Moo-yeom's father was the killer, he is extremely prejudiced against Moo-yeom, which makes for a combative working relationship. He also hiding grief of his daughter's death.

Kim Min-jung as Maria Oh

A psychiatrist with a mysterious double life and a suspicious curiosity for all things Gap-dong.

Kim Ji-won as Ma Ji-wool

A 17-year-old high school student and webtoon artist with the pen name "Matilda." Ji-wool becomes pivotal to the case when her webtoon titled The Beast's Path ends up foretelling the crimes. When she becomes the killer's next target, it also serves as a set of clues to find him.

Lee Joon as Ryu Tae-oh

An inmate of a prison psychiatric hospital, who becomes a barista after his release. With a genius IQ of 150, his excellent and detailed memory may prove valuable to cracking the case, but he also happens to have the disposition to be a dangerous psychopath, and considers Gap-dong his god and hero.

Supporting characters

Jung In-gi as Cha Do-hyeok, the police section chief

Kang Nam-gil as Han Sang-hoon, a profiler

Jang Gwang as Jinjo, a monk

Jo Ji-hwan as Lee Hyung-nyeon, Moo-yeom's partner and wife

Choo Soo-hyun as Oh Young-ae

Min Sung-wook as Nam Ki-ri

Jung Won-joong as Park Joong-goo

Jang Hee-soo as Kim Young-mi, Maria's mother

Yoon Kyun-sang as the youngest detective.

Hyun Woo as young Cha Do-hyeok

Hong In-young as Hong Sung-hee, a reporter

Seo Joo-hee as Ji Hwa-ja, Ji-wool's mother

Yoo Eun-ho as Yang Seon-joo, Cheol-gon's daughter

Lee Go-eun as young Seon-joo

International broadcast

It aired in Thailand on Workpoint TV beginning March 9, 2015.