Kim Hee-woo is a passionate and upright prosecutor who is murdered while investigating a powerful and corrupt politician, Cho Tae-seob. After his death, he is given a miraculous second chance at life by a mysterious grim reaper, waking up as a high school student with all his memories intact. Armed with the knowledge of his past life and future events, he resolves to meticulously dismantle Cho Tae-seob's corrupt empire from the ground up. As he navigates his second life, Hee-woo strategically builds alliances, accumulates wealth, and climbs the ranks of the legal system to become a prosecutor once again. The series follows his calculated journey of retribution, highlighting the complex power dynamics of South Korean politics and the moral dilemmas he faces while trying to change the course of history without losing his own humanity.