After the tense encounter with Ju-yeong at the office, culminating in Dong-ju's furious punch that shattered the window into a thousand pieces, episode 4 of "Good Boy" kicks off with the rivalry between these two formidable adversaries reaching a boiling point. The shattered glass serves as a catalyst for Man-sik's stern rebuke towards his junior, especially when they receive a staggering repair bill of 3.3 million won.
The underlying tensions persist between Jong-hyeon and Dong-ju, who can't seem to agree on the best course of action for their case—or who's trying to win Han-na's affections. Consequently, the team splits into two, each covering more territory in hopes of making progress.
Dong-ju's jealousy ignites when he sees Han-na paired with Jong-hyeon, prompting him to step in and take her place. However, their search is plagued by constant clashes, hindering their progress significantly. Meanwhile, Jong-hyeon persists into the night, scrutinizing CCTV footage and noticing an abundance of cigarette butts scattered about.
Elsewhere, Han-na and Jae-hong track down the elusive Oh Jong-gu, the man who received the bloody watch from Ju-yeong in the previous episode. They confront him directly about his involvement in Gyeong-il's death, but he remains composed and evasive.
On their way back, Han-na is intercepted by Hwang Kyung-chul, who harbors crucial information for her. He revisits the dark chapter from 2008 when a Russian mafia member was gunned down, with her father overseeing the crime scene. He presents her with a folder brimming with details about the incident, revealing that her father's suspected cause of death—a gunshot to the head, likely by a mafia member—was never solved, despite the evident connections.
Man-sik embarks on his own sleuthing regarding the pawnshop watch, which leads him to Gwang-se, a man adorned with a bold bald eagle tattoo. Once renowned for his expertise in smuggling cars, Gwang-se also boasts connections to the notorious Golden Bunny gang. He eventually spills the beans about Monkey, a mastermind in the country's car smuggling underworld. Complicating matters further, there's an insider at Insung Customs aiding Monkey, who turns out to be none other than Ju-yeong. Monkey still retains possession of the car, necessitating the team's utmost discretion; any loud whispers or station-wide revelations could prompt Ju-yeong to cover his tracks before they can crack down on the operation.
Consequently, the team devises a cunning plan to entice Monkey with a bait car. Unfortunately, the most likely candidate for Monkey's interest belongs to the Commissioner. With Gwang-se's assistance, they manage to secure the vehicle and set their plan in motion.
During their stakeout, Dong-ju and Han-na find themselves in an awkward predicament, but they quickly regroup with the others, much to Jong-hyun's chagrin. The operation kicks off, and they rush into the warehouse with bated breath. However, their efforts are undermined by Dae-yong and his cronies, who swoop in to steal the limelight by busting Monkey and his smuggling operation.
Despite a fierce skirmish, Monkey manages to slip through their fingers. But he's discovered by the roadside shortly after, the victim of a professional hit, a screw-like knife plunged into his neck. This grim discovery hints at a professional killer covering his tracks. Forensic analysis also unearths cigarette butts similar to those found near the CCTV cameras at the dock, but they still find themselves at another impasse.
Meanwhile, Man-sik is burdened with the daunting responsibility of confronting the Commissioner's fierce displeasure, particularly when the latter discovers the wrecked car. Despite these formidable obstacles, the operation manages to uncover the elaborate scam, leading to the arrest of quite a few henchmen. Inevitably, Commissioner Cho claims all the glory for this triumph!
Subsequently, Jong-hyun ponders with the group, postulating that this entire ordeal is intricately linked to both the Russian mafia and a drug trafficking ring operated by an armed Filipino syndicate. Regrettably, they fail to locate Ju-yeong's car within the warehouse. However, they do discern that Monkey required an insider to manipulate the paperwork, clarifying why Lee Jin-su met his untimely demise. He stumbled upon Ju-yeong's scheme and paid the ultimate price for his discovery. The documents he unearthed were also incinerated, a scene we witnessed earlier with Ju-yeong.
Enraged, Ju-yeong vents his fury on the Section Chief during a confrontation in the bathroom. Time is of the utmost importance, and in a bid to locate the contraband, the group hastens to the dock, scrutinizing each shipping container meticulously. They have until 7 pm to find Ju-yeong's car, and while Dong-ju engages Ju-yeong to buy the team some precious time, they eventually track down the vehicle.
A thrilling chase ensues, with the team working in unison to apprehend Ju-yeong as he weaves through the streets, narrowly missing obstacles. Han-na courageously stands in the middle of the road, attempting to halt his reckless spree. Ju-yeong spots her and, in a moment of conscience, decides to avert a collision, leaping from the roof and crashing into the windshield.
Ju-yeong is apprehended, and it seems highly unlikely that he will catch his flight. However, Dong-ju has succeeded in thwarting his plans, at least temporarily.
