Continuing from the previous series, under Lang's leadership, DIE continues to solve bizarre cases and ultimately gets "honorably disbanded." Apart from Jingle taking a maternity leave and Fee Sir retiring back to his hometown in Scotland, the rest of the team returns to their previous workplaces. However, their quirky personalities and styles remain unchanged, continuing to give headaches to their superiors and facing exclusion at work.
During a large official event, the former members of DIE gather for various reasons to carry out tasks. Coincidentally, Jingle, who was passing by with her baby, instinctively arrests her arch-nemesis Big Mouth Ying engaged in illegal activities, accidentally trespassing into a restricted area. This triggers a chain reaction causing chaos among the group, embarrassingly making the top police officer lose face on the spot... Blame falls on the top officer, prompting a high-level police meeting. Lang's immediate superior, Law Yau Hang, to get rid of his troublesome subordinates once again, proposes the reformation of DIE, concentrating these troublemakers who can't be fired back together, letting them fend for themselves. Since the original DIE supervisor Fee Sir has retired, Hang is forced onto the stage, compelled to take up the important role of supervising DIE.
Upon hearing about the reformation of DIE, Jingle becomes very eager and requests to end her maternity leave and return to work as soon as possible. But due to Lang's patriarchal mindset, he uses small tricks to make Jingle agree to take a year off and become a full-time mom to take care of the baby. Later, when Lang's tricks are discovered by Jingle, she refuses to be manipulated by Lang and decides to apply for reinstatement herself. Jingle returns to the Major Case Team and collaborates with newly arrived high achievers. Their contrasting characters and styles clash like Mars colliding with Earth. Moreover, since Jingle had previously offended the top officer, her superior fears that Jingle will drag down the Major Case Team, so they use an excuse to transfer Jingle back to DIE. Back at DIE, Jingle entrusts her baby to her extended family for care, but this causes disagreements between Jingle’s mother and grandmother over how to take care of the baby, leading to constant quarrels day and night. To avoid family disputes, Jingle's father Nan orders Jingle to take care of the baby herself. Therefore, Jingle brings her baby to work, where the DIE team takes turns looking after the baby, generating endless jokes...
Hang, in order to quickly get rid of the troubles, continuously overworks everyone and deliberately splits DIE, forcing Lang and Jingle to lead separate teams to compete in solving cases. Initially, Lang and Jingle just do their respective duties, but Lang, with his supernatural intuition, repeatedly solves cases, leading his team far ahead in performance... Meanwhile, Jingle unintentionally discovers that her baby seems to have inherited some inexplicable abilities from Lang, often able to predict answers to certain things, helping Jingle make correct choices and repeatedly turning danger into safety. Doubtful, Jingle temporarily does not inform Lang about this matter... To avoid dragging her subordinates into being unjustly dismissed, Jingle secretly uses her baby's special abilities to assist in investigations, impressing others. However, Lang eventually finds out and is very dissatisfied, fearing it might adversely affect the baby's growth. He strongly opposes Jingle abusing the baby's special abilities, adding more tension to their relationship. At this time, Lang encounters his first love, Man Chuchu, and works harder to help clear her of murder charges, making Jingle jealous and causing a cold war between the couple... Unexpectedly, "Siu Yi" reappears, but this "Siu Yi" is not the real Siu Yi... Due to thinking about her all day, Lang dreams of meeting Siu Yi, who surprisingly warns him in the dream, pointing out that the life-and-death fate between Lang and Jingle remains unresolved. Although having a baby temporarily averted disaster, as the baby grows older, misfortune will return, and Jingle will face mortal peril again. Just as Lang is half-believing this, the big villain from the previous series, Chan Hoi Wing, reappears before Lang and Jingle... It turns out this person is actually Wing's twin brother, Chan Hoi Wah, who had been secretly hospitalized in a foreign psychiatric hospital due to mental issues and is now returning to enact his revenge plan...