In 1986, in the province of Gyunggi, in South Korea, a second young and beautiful woman is found dead, raped and tied and gagged with her underwear. Detective Park Doo Man and Detective Cho Yong Koo, two brutal and stupid local detectives without any technique, investigate the murder using brutality and torturing the suspects, without any practical result. Then Detective Seo Tae Yoon from Seoul comes to the country to help the investigations and is convinced that a serial killer is killing the women. When a third woman is found dead in the same "modus-operandi", the detectives find leads of the assassin.
Gyun Woo is a college student, more interested in picking up girls, drinking with his buddies and avoiding his nagging mother whenever possible. While riding the subway, a drunken girl then changes his fate forever. She's nearly unconscious on the train and vomits on an older guy. She then leans over to Gyun Woo and everybody assumes she is his girlfriend! Gyun Woo soon finds himself in a relationship he didn't ask for, but soon unable to forget this sassy girl.
Kim Sa Ra was the daughter-in-law of the biggest law firm in South Korea, but she was betrayed by her husband and lost everything. After that, she began working as a divorce troubleshooter. She is now the team leader at the divorce settlement office Solution. She punishes bad spouses and provides help for those who find themselves in unfair divorce situations.
She works with Dong Ki Joon. He is Sa Ra’s business partner and an advisory lawyer at Solution. Before coming to Solution, he was an excellent prosecutor who had the nickname of "German Shepherd." He picked up the nickname because of his persistence and keen intuition, but Ki Joon left the prosecutors' office for an unknown reason. Sa Ra and Ki Joon work together for people who are suffering through difficult divorces.
On the Chinese side of the China-Russia-North Korea border, in the Yanbian, Korean Autonomous Prefecture, Ku Nam toils his days away as a taxi driver. When he's not working he's often found in the gambling halls. Ku Nam is now in serious debt. His wife left to work in South Korea and promised to send money back. He has yet to hear from her and he is tormented by nightmares of her having an extra-marital affair. Making matters worse, Ku Nam is fired from his job and debt-collectors take most of his severance pay.Dog seller and underworld crime boss Myung Ga offers him a deal. If Ku Nam goes to South Korea and successfully carries out a hit he will get paid $10,000 USD. Ku Nam accepts the deal and leaves for Korea on a rickety fishing boat with $500 dollars for his expenses.When Ku Nam arrives in South Korea he carefully scopes out his target for days, while also searching for his wife. When the time arrives for Ku Nam to take out his target, a string of unexpected events occurs leaving Ku Nam desperately looking for a way out. Meanwhile, the cops, Korean mafia, and the Chinese mafia all frantically search for Ku Nam.
During his school days, Yeo Jeong Woo always placed first in academics and he studied at the top medical school in the country. Jeong Woo is now a popular plastic surgeon. His life goes smoothly, but, due to a mysterious medical accident, his life is pushed to the edge. At this time, he meets Nam Ha Neul. She was a rival in his past and he meets her at the lowest point in his life.
Ha Neul works as an anesthesiologist. When she was growing up, people called her a genius due to her extreme intelligence. She studied hard and became a doctor. Her life consists of only work and studying. She doesn't have any time to experience fun. One day, Ha Neul realizes she isn’t happy with her life and she wants to make a change. At this time, she meets Jeong Woo during one of the worst moments in her life. They comfort each other and a romantic relationship blossoms between them.
Jin Yi Soo has everything in life. Being a third-generation conglomerate, he never requires others’ assistance. However, things start changing when he gets entangled in a case.
Jin Yi Soo joins the violent investigative team at the Kangha Police Station that specializes in catching robbers. He aims to use his wealth and personal connections to his advantage. He works under Detective Lee Kang Hyun. Kang Hyun is dedicated and a smooth-talker and doesn't care for Yi Soo's presence when they begin working as partners.