Kim Sun-woo is an enforcer and manager for a hotel owned by a cold, calculative crime boss, Kang who assigns Sun-woo to a simple errand while he is away on a business trip; to shadow his young mistress, Hee-soo, for fear that she may be cheating on him with a younger man with the mandate that he must kill them both if he discovers their affair.

After Gyeong-bae's son is kidnapped, he receives a call from the kidnapper asking for 100 million won. The detectives are teamed up for the case, yet the culprit gets away at every opportunity.

A deep secret from Kim Jin-woo's past is slowly eating away at him and making him act more and more irrationally. He loses his position as a philosophy professor due to his erratic behavior. He and his wife turn to a psychiatrist to get to the root of the problem.

Sun Woo Sumi is a lecturer at a French-language school after studying in France, but she has not forgotten the nightmare from seven years ago. She was assaulted by five men during her first year of college with Jin Woo. At that time, Sumi decided to study abroad. Jin Woo, a police officer, tries to recover her mental and physical injuries.

A wily safecracker is forced to help a mob boss pull off a $150 million heist, but smells a double-cross in the works.

A young boy during the midst of Korea's development boom learns a mysterious man roaming around his neighborhood may be more than meets the eye.

Set 3 years after the first season, members of the National Security Service (NSS) team, including Jung Yoo Gun, Ji Soo Yeon and other agents attempt to pull the curtain on mysterious group IRIS. Agent Yoo Gun is the leader of the NSS TF-A team. While he goes up against Baek San, Yoo Gun becomes involved in a case which changes his fate forever.

Governor Heo, worried over the plague that's sweeping the country, rebukes the Kus who make amulets to ward off evil. Heo castrates the husband when he makes superstitious claims and takes the wife as his mistress. Heo continues to be tormented by hallucinations and nightmares and begins to blame it on the Kus' curse. He kills the couple at their reunion and unable to ward off his bad karma, dies from leprosy.

A U.S. soldier comes to Korea and tracks down his biological father in jail.