Kim Hee Woo came from an inauspicious start as a low-grade high schooler to work his way up through university and finally pass the bar examination. His relentless hard work has finally paid dividends, and he has become a public prosecutor. During the course of his investigations, he must conduct a probe into a politician suspected of corruption. But his investigation is abruptly ended when a mysterious man kills him. However, he later comes to, finding that he is actually alive. Restored to the mortal realm, he finds that he must return to university and complete his academic journey again – while he tries to discover the truth about what happened to him.

Set in the late 1920s, The Age of Shadows follows the cat-and-mouse game that unfolds between a group of resistance fighters trying to bring in explosives from Shanghai to destroy key Japanese facilities in Seoul, and Japanese agents trying to stop them.