Deliveryman Jong-su is out on a job when he runs into Hae-mi, a girl who once lived in his neighborhood. She asks if he'd mind looking after her cat while she's away on a trip to Africa. On her return, she introduces to Jong-su an enigmatic young man named Ben, who she met during her trip. One day Ben tells Jong-su about his most unusual hobby.

At his mother's 70th birthday party, Yong-nam runs into Eui-joo, who rejected him in college. When the city is engulfed in toxic gas from a terrorist attack, the two must find a way to escape using all the techniques they learned in their college rock climbing club.