The Trigger depicts a professional hit man/assassin (Ni Ming Ran) hired to take out a target. However, his girlfriend's (So Yun Ko) pregnancy gives him second thoughts. He decides that after this job, he will renounce his profession and turn himself in. After his release from prison, he finds his girlfriend married. Bent on revenge, he hooks up with another ex-con he met in prison, a younger man unjustly incarcerated. They plan the job, but his hate disappears when he sees his old girlfriend and his daughter leading happy, normal lives. Unfortunately, determined to dish out justice, his younger partner kills the girl who got him put away.