Mistress

Four female friends in their 30's become involved in a series of murders.

Se-Yeon (Han Ga-In), Eun-Soo (Shin Hyun-Bin), Jung-Won (Choi Hee-Seo) and Hwa-Young (Goo Jae-Yee) have a dead man’s body in front of them. Jung-Won looks at the scented candle in her hand and blames the scented candle.

2 months prior, Se-Yeon runs a cafe. She has a daughter. Her husband died 2 years earlier, but his body was never found. She then receives a phone call without a caller ID number. The caller plays a song that was her husband's favorite song. Song-Hoon (Lee Hee-Joon) approaches Se-Yeon. His daughter attends the same kindergarten as Se-Yeon's daughter.

Se-Yeon has three close friends: Eun-Soo, Jung-Won and Hwa-Young. Eun-Soo works as a psychiatrist. One day, her patient Sun-Ho (Jung Ga-Ram) tells her that he is looking for his dead father's mistress. He believes that the mistress killed his father. Eun-Soo does not tell her client that she is the one who had the secret affair with his father. Eun-Soo also has another secret.

Jung-Won is a high school teacher. She is married to famous chef Dong-Seok (Park Byung-Eun). He seems like the perfect husband. Dong-Seok wants to have a child badly, but Jung-Won doesn't know the real reason why her husband wants a child. The real reason is so Dong-Seok can have material for a reality TV show. Meanwhile, Min-Gyu (Ji Il-Joo) is a temporary teacher at the same high school where Jung-Won teaches. He tells her that he likes her.

Hwa-Young works as an office administrator at a law firm. She enjoys her single life and she doesn't want to be tied down with one man. One day, a female client comes and requests that someone secretly follow her husband Tae-O (Kim Min-Soo). That man is Hwa-Young’s ex-boyfriend.