After his business goes bankrupt, 30 something Kyung-Min (Oh Jung-Se) kills his wife impulsively. Hiding his anger, he seeks out his former middle school classmate Jong-Suk (Yang Ik-June). For the first time in 15 years they meet and hiding, their own current situations, they talk about their school days.

At school, they were classified by their wealth and grades. Kyung-Min and Jong-Suk were at the bottom and were the 'pigs'. They were bullied by a ruling class of 'dogs'. This bullying led to a harrowing incident 15 years ago at the school, and they return to the site where the most shocking truth of what happened there is finally revealed.