An ordinary businessman in his forties, Jang Ga Pil returns home one day to find his daughter attacked by teenage hoodlums, including school boxing star Kang Tae Wook. Realizing that he has no background and money to fight back, he plans to stab Kang on the way to school. This fails miserably, but another student named Go Seung Suk agrees to teach Ga Pil to fight - in only 45 days.