就讀國中的林友達，因為父親曾肇事逃逸的往事被揭露，因此遭到好朋友們的霸凌，這些加諸其上的暴力逐漸滲入林友達內心，在向外求援卻一再被誤解曲解後，林友達轉向生活中最暴力的角色：手握屠刀的鮮肉餅攤老闆。一封封寫給父親的求救信，最後交給鮮肉餅老闆，林友達為了復仇做了最激烈的決定。只是獨自面對回憶、罪惡感、與心頭難以消散的憤恨，林友達的內心世界也被暴力侵入，無法平息。

Lin, a young boy bullied in school. Classmates accuse Lin's father of being a serial killer since he caused a hit-and-run accident several years ago. Lin turned to meat pie peddler who used to be a gangster. Lin stole his mother's money and asked the peddler to kill four of his classmates. But the peddler didn't take revenge for Lin; he ran away. Because of this, Lin transfers to a new school, a transformed person. From the scrawny boy bullied around, he has become the ring leader of a gang of bullies.