Episode Summary
This episode juggles multiple intersecting plotlines. Lin Qiangfeng's pursuit of a fugitive, Lao Gui, inadvertently leads to the death of Sang Bo, the woman who murdered his partner four years prior. A major police sting operation to intercept a drug shipment fails, revealing a mole or a miscalculation. In parallel, Lu Shaohua resorts to bribery to advance his career, while Jin Yongxiang is blackmailed by the dangerous Luo Bingzhang over past crimes connected to the recent murder of Xu Desheng.

Spoiler Alert
The Narcotic Operation: Episode 4 Spoilers
The episode opens with a flashback to four years ago. Lin Qiangfeng reports to Captain Qi of the Linbian Anti-Drug Division after completing an undercover assignment. The mood is somber, as his colleague, Li Baichuan, was killed during the operation to capture a figure known as "Brother Hu." Captain Qi suggests Lin take a break, but Lin, tormented by the brutal memory of Li's death, wants to return to work immediately.
In the present, Sang Bo and Miao Lun are tracking a woman named Qingqing. They confront her, demanding to know the whereabouts of a man called Lao Gui. They locate Lao Gui's hiding spot, and he flees to the roof, barricading the door behind him. Meanwhile, Lin Qiangfeng's team, having duplicated the pager of a man named Xu Desheng, sees an incoming message from Lao Gui. Lin heads to the public phone booth mentioned in the message.
Unable to get onto the roof, Sang Bo and Miao Lun decide to wait below. Suddenly, a murder occurs at the nearby phone booth. Lin Qiangfeng and his team rush to the scene. As they investigate, Lao Gui attempts to climb down from the building. Sang Bo spots him from a nearby theater and fires her gun, causing him to fall. In her haste to chase him, she slips and falls from the building to her death. When Lin arrives, he finds Sang Bo's body and recognizes a tattoo on her neck, identifying her as the one who killed his partner, Li Baichuan.
A separate storyline follows Lu Shaohua. He is approached by his old master, who needs to borrow money for his wife's medical treatment. Lu promises to help. Later, the factory director confronts Lu about his lax work ethic and side businesses. As a punishment, Lu is assigned two months of night duty. The director then hints that there's an opportunity for an employee to get a prestigious position within the "system," but another colleague is the favored candidate. Understanding the implication, Lu offers the director a bribe to secure the recommendation.
At the police station, Tan Qinglin reports to Chen Qingquan that Xu Desheng's murder was a revenge killing intended to intimidate Lao Gui. Chen orders Tan to solve the case quickly. When Chen inquires about Lin Qiangfeng, Tan dismisses him as a troublemaker.
Another plot involves a powerful figure named Luo Bingzhang confronting Jin Yongxiang. Luo reveals he knows that a branch from a tree, which was cut down due to the negligence of a gardener hired by Jin, was used as the weapon to murder Xu Desheng. Luo also knows that Jin used Xu for drug trafficking. He blackmails Jin for two million within three days.
Meanwhile, police officer Li An is tracking a major drug shipment. He and his assistant are hiding in a timber truck set to deliver 10 kilograms of meth to a trafficker named Meng Hanchiu. However, the surveillance goes awry. Meng Hanchiu doesn't show up for the deal, and a search of the supposed drop-off location at a lumber mill yields no drugs. Li An's team realizes they've been deceived after a three-month-long stakeout.
The episode concludes with Miao Lun learning of Sang Bo's death over the phone and vowing to get revenge.