Police detective Fok Chi-ho heads a dedicated team tasked with tracking down a violent armed robbery gang. Despite their efforts in capturing the majority of the gang, their elusive leader manages to evade them, leaving no links connecting him to the crime, and walks free without facing charges. This unsettling incident deeply shakes Fok's belief in the police force, leading him to take a drastic step: he resigns and turns his focus toward studying law.
Fast forward seven years, Fok joins the Department of Justice and embarks on a new journey as a public prosecutor. Under the guidance of his mentor, Bao, he tackles his first high-stakes case involving drug smuggling. The defendant, Ma, has found himself entangled in a web of legal troubles after receiving a suspicious parcel from Brazil that contains a kilogram of cocaine. Ma firmly asserts his innocence, claiming that he only lent his address to his friend, Chan, who had promised to assist him financially to ease his family's debts.
However, Ma's defense lawyer, Li, and legal executive, Au, mislead him into a state of panic, convincing him that his chances of conviction are high and nudging him towards a guilty plea in exchange for a supposedly lenient sentence. Reluctantly, Ma and his grandfather, Uncle Ma, agree to this misguided strategy. When Li approaches Fok for discussions on the plea deal, Fok becomes wary of the terms, especially since they allow Chan to exit the situation completely unharmed while Ma bears the full brunt of the guilt. Despite Fok's reservations, chief prosecutor Yeung accepts the plea bargain, convinced it is the best route for securing a conviction.
While imprisoned, Ma encounters other inmates who reveal the treachery he has endured, prompting him to reconsider his guilty plea for fear of losing touch with his grandfather once again. Believing in Ma's innocence, Fok supports him in changing his plea, challenging the discontent of Yeung. In the initial trial, Au and Li testify against Ma, but even as Ma’s lawyer strives to reveal the deceit behind the negotiations, the absence of substantial evidence leads to the rejection of his claims. As Fok navigates the courtroom, he starts to defend Ma by interrogating his own witnesses. The judge attempts to silence Fok, leading to a confrontation where Fok passionately argues that the prosecution should prioritize genuine justice over mere conviction rates. Unfortunately, this vocal defense turns the jury against Ma, resulting in Chan's acquittal while Ma receives a harsh sentence of 27 years for drug smuggling on account of having shown no remorse.
Realizing the gravity of his error, Fok is determined to assist Uncle Ma, who initially rebuffs his efforts. However, Fok eventually saves Uncle Ma from an assassination attempt, prompting the older man to share vital information. Uncle Ma reveals that they had hired Li based on a referral from Lau, the proprietor of the restaurant where Ma worked. Following the assassination attempt, Bao agrees to help Fok investigate, leading them to uncover that Prosecutor Yeung has overseen numerous cases involving Au in a dubious fashion.
As their inquiry unfolds, Bao cleverly infiltrates a nightclub owned by Lau and eavesdrops on a conversation that unveils a shocking familial connection: Lau and Chan are half-siblings. It becomes clear that one brother has been soliciting individuals to lend their addresses for illicit drug trade, while the other has been masquerading as a benevolent legal advisor, guiding them into a trap through the actions of Li and Au, who manipulate the legal process to ensure they take the fall.
Fok supports Uncle Ma in filing for an appeal, but tragedy strikes when Uncle Ma is murdered at a cha chaan teng. As the half-brothers remain the only viable leads, Fok seeks out other victims to build his case and ultimately finds a courageous girl willing to testify against Lau. Realizing the walls are closing in on their scheme, Au attempts to convince Lau to turn himself in, but he meets a grim fate at the hands of Sang and Tung, associates of Au’s within the underworld.
While this turmoil unfolds, Fok confronts Yeung and discovers a miscommunication rather than guilt. They manage to set aside their differences for a common goal: justice.
During the retrial, Yeung takes on the role of prosecutor and strategically buys time for Fok, who is on a mission to locate the elusive Chan. With the assistance of Inspector Lee, Fok's former protégé, they manage to track down Chan, persuading him to provide testimony against Au. However, their efforts lead them into danger, as they are attacked en route to the courthouse, injuring Lee severely. Undeterred, Fok and Chan proceed to the courthouse on the MTR, where they confront Sang’s henchmen. After an intense showdown, Fok successfully dispatches the assailants and ensures Chan can deliver crucial testimony against Au.
In the end, justice prevails as Ma is exonerated while Au and his criminal network face the legal consequences of their actions. This compelling journey highlights the essence of perseverance and the unwavering pursuit of justice in the face of adversity.
