Tells the story of a man named Jang Hyuk, who wants to have both work and love, his girlfriend Da Eun, and Bo Young, a woman he meets in a new environment. It is said to be a refreshing romantic comedy about the complicated relationships between three people who are experiencing different emotions.
This film is about a group of high school students and teachers who get locked in the school after the swimming instructor is murdered. In South Korea, the high school student and swimmer Jeong Tae Yeon is found dead in the pool, apparently a suicide. Two years later, teacher Park Eun Soo joins the high school, where Tae-yeon's stepsister Lee Se Hee is haunted by nightmarish visions and is bullied by the student Eom Ji Yoon. Eun Soo finds it difficult to get respect in the classroom and is backed up by an older teacher, Cha. Se Hee and her classmates are selected for an elite "study camp" held at the school during the summer break where 30 students study for their university entrance exams. The school's swimming trainer is murdered in the showers, and the words "When an innocent mother is killed, what son would not avenge her death?" found scrawled on a blackboard. A voice warns the students that they'll all be killed unless they can answer who is the murderer and why. The students and teachers find they're locked in the school when more deaths begin to happen.
Eun Ah lost her family at the hands of a serial killer. She is now mentally and physically destroyed. Eun Ah then decides to get revenge. She enlists the help of four people marginalized by society including a North Korean defector, ex-gang member and a person heavily in debt. All four persons need organ transplants. Eun Ah's plan is then set in motion.