Due to his history of theft in the past, Lin Kuan is falsely accused of stealing from his high school classmate. To prove his innocence, Lin enlists his friend Xiao Bing to make a plan that will clear his name. However, heir seemingly perfect plan takes a turn that pushes Lin to a dangerous edge.

Beat Him Up focuses on issues of bullying and mental health, exploring the profound ways in which guilt and repressed emotions can change and ruin lives. Set in a Taiwanese high school, the film follows the weak-willed Zhang Shi-hao, who becomes jealous when a new transfer student called Lin Yu-en steals his girlfriend and eventually gets her pregnant. Although Zhang is too meek to take revenge, his best friend A-Yang sets up a brutal attack on Lin with a group of other boys. The timid Zhang joins in, releasing his pent up anger and frustration, feeling a sense of satisfaction afterwards, which turns to shock and guilt when Lin collapses and dies during a PE lesson the next day. Blaming himself, the tormented Zhang decides to confess, though fate has something else in store for him. Through Zhang's personal journey, the film examines the process of redemption, asking the question whether guilt can be a positive force, pushing us to rise above our shortcomings.