Jong-su bumps into a girl who used to live in the same neighborhood, who asks him to look after her cat while she's on a trip to Africa. When back, she introduces Ben, a mysterious guy she met there, who confesses his secret hobby.
After Ben mentions that he burns down an abandoned greenhouse about every two months and that he's planning on burning one very close to Jong-su's home, Jong-su starts to pay attention to likely targets around him. Then he loses contact with Hae-mi and starts to look for her. Her luggage is in the apartment, unusually tidy and clean, but her cat, whom Jong-su fed many times but had never seen, also has vanished. Jong-su confronts Ben, who is dating a new girl who works in retail and claims that Hae-mi has not returned his calls either. Jong-su starts to stalk Ben while finding out more about Hae-mi through various leads he chases--did she make up stories or not?
One day, Jong-su follows Ben into the countryside. But instead of checking out old greenhouses, Ben is looking at a secluded reservoir. Jong-su meets up with his own mother who abandoned the family when he was ten, and promises to get money to help her pay her debt. Jong-su sells the only cow the farm still has.
Ben finally catches Jong-su staking out in his truck nearby and invites him up to his apartment to attend his party. Jong-su sees Hae-mi's pink watch in the bathroom and confirms that the cat that Ben has adopted is indeed Hae-mi's. Jong-su abruptly leaves.
When Ben shows up near an abandoned field to meet Jong-su, the latter fatally stabs him with one of his father's hunting knives, and then douses gasoline over Ben's sports car with the body inside, just like Ben described how he would burn down those expendable greenhouses.