Full spoilers follow.
The set-up. Jo Pil-ho, a corrupt Ansan homicide detective, recruits Han Ki-chul as an accomplice for a scheme involving the police storehouse. When Ki-chul enters, a massive explosion kills him and incinerates a cache of highly classified evidence. Pil-ho survives, and the prosecution immediately treats him as the man behind it. The crucial reframing is that Pil-ho was never the author of the plan he thought he was running — his petty criminality made him the perfect patsy for people who needed that evidence destroyed and needed someone credible to blame.
The conspiracy. Pulling the thread leads to the Taesung Group and the officials protecting it. Pil-ho's only route to proof runs through Mina, a teenage girl connected to the affair, and their partnership — initially exploitative on his side and mistrustful on hers — becomes the spine of the film. The Sewol ferry thread runs beneath all of it: the characters are mourning one of their own, and the conspiracy is presented as the same species of institutional lying that the city has already survived once.
Mina's death. Having lost her will to live under the accumulated weight of what has been done to her and what she knows, Mina jumps from a building. This is the film's hinge. It removes any possibility that the story is a rescue narrative and converts Pil-ho's investigation — which was, until then, still partly about saving his own skin — into pure vengeance. Every earlier moment of him using her is retroactively poisoned.
The climax. Pil-ho fatally shoots Kwon, then shoots Jung in the head, before being shot himself by Kim. He survives; his actions expose Taesung Group's corruption. But he is arrested for murder, and the film's final image is of a man broken and driven out of his mind by the whole ordeal.
What becomes clear afterwards. The title's "dawning rage" is not an awakening of conscience but the moment grief stops being survivable and becomes action. The film systematically withholds every satisfaction its genre promises: the corrupt are exposed but the exposure changes nothing that matters, the girl is not saved, and the antihero is not redeemed — he is simply used up. Read against the Sewol context the director explicitly built in, the ending argues that the truth coming out years later, to a public already exhausted, is not justice. It is just the record being corrected over a grave.