Episode 4 of A Killer Paradox kicks off with a cozy team dinner among colleagues.** The boss, Prosecutor Ji, hands out his business cards to the group before excusing himself to head home. He summons a driver, mistaking the hooded figure in an "Only For Heroes" sweater standing near his car for the actual chauffeur. Halfway through the journey, Ji is jolted awake by a call from the real driver, realizing with a shock that he's being taken in the wrong direction. Suddenly, lights flash ominously inside the car, and we cut to a chilling vision: a lifeless body drifting down a river.
Elsewhere, Yeong visits the convenience store owner, who surprisingly withdraws his complaint against Tang, disclosing that Tang's family had settled the debt owed. Meanwhile, Chung-jin bids farewell to his life at the police station as a special investigative unit is formed to crack the murder cases. Four months pass, yet the unit remains at a dead end. Nan-gam scoffs, branding the entire operation a publicity stunt. Overhearing his skepticism, the female unit leader confronts him, their argument underscoring a fundamental divide: Nan-gam believes all the murders stem from a single perpetrator, while she remains unconvinced.
In a room adorned with superhero memorabilia, a young man named Roh Bin engages in an online discussion about a murder case, hinting at his prowess as a profiler. Nan-gam visits Bin, laying out the details of several murder cases. Bin ponders the possibility of a serial killer's involvement. Unbeknownst to Bin, Nan-gam's colleague eavesdrops on their conversation. When Bin slips and reveals his unauthorized access to the prosecutor's network, Nan-gam swiftly orders his colleague to escort Bin to the station.
At the station, Nan-gam persuades his captain to let him handle Bin personally, betting that Bin holds crucial information. Despite a lack of evidence, they eventually release Bin, but this seems to be part of Nan-gam's master plan. During the ride back home, Nan-gam confides in Bin about the investigation's stagnation, urging him to share any insights he uncovers.
Later, while grabbing a bite at the convenience store, Nan-gam spots Rex, Yeo-ok's dog. Intrigued, Nan-gam tails Rex to Yeo-ok's residence, setting the stage for further unraveling of the intricate mystery.
A visitor arrives at Roh Bin's abode, bearing a delivery of sustenance, but to Roh Bin's surprise, it is Tang who stands at his door. They exchange glances that hint at a shared purpose, and Roh Bin cautions Tang to proceed with discretion. Meanwhile, outside, Nan-gam's fellow officer intercepts Tang, inquiring about the apartment for which he is making the delivery.
In a nearby vehicle, Nan-gam informs Yong-jae that Roh Bin once served under the very murderer Nan-gam is trailing. Oblivious to Tang's conversation with the officer, the latter joins Nan-gam in the car, relaying that the 'delivery man' claims never to have laid eyes on Roh Bin. Nan-gam, who witnessed Roh Bin accepting the delivery, knows this to be a falsehood. He promptly orders the other officers to pursue Tang without delay.
Yong-jae and another officer set off in chase of Lee Tang, while Nan-gam storms into Roh Bin's residence, demanding to know if Roh Bin has been orchestrating the selection of victims for Tang. He presses Roh Bin to divulge Tang's whereabouts. Yong-jae soon returns with the delivery man, but it is the wrong individual. The captain then calls Nan-gam, his voice dripping with fury.
It transpires that Roh Bin has installed cameras throughout his apartment, and videos depicting Nan-gam's brutal assault on him have been disseminated across the internet. The captain is incandescent with rage. More policemen converge on Roh Bin's doorstep.
A flashback to four months prior unfolds. Tang packs his belongings and bids his family farewell via a letter, announcing his departure to Canada without a proper goodbye. He vows to return a better man but finds himself sleeping at a railway station instead. He searches online for 'Only For Heroes' to no avail. His days blend into a routine of riding trains until one day, Roh Bin approaches him, introducing himself as the elusive 'Only For Heroes.'
Roh Bin escorts Tang back to his place and proposes a collaboration, presenting himself as a trusty sidekick akin to Watson or Robin—a moniker he officially adopted by legally changing his name. He reveals a startling familiarity with Tang's dark past, detailing each murder with chilling precision. Moreover, Roh Bin is privy to Tang's enigmatic superpower: those whom he eliminates are deemed unworthy of life, and all incriminating evidence inexplicably vanishes. With the promise of wealth, Roh Bin entices Tang to embark on a joint mission to uphold justice.
The following morning, their conversation delves deeper into Tang's extraordinary abilities. Roh Bin mentions two former partners, one of whom Tang has already encountered—Bu-il. The other, he warns, is a figure Tang would prefer to avoid. Intrigued, Tang searches behind a shelf as instructed, uncovering a clandestine chamber laden with armaments, dossiers, and a jacket inscribed with "Only For Heroes." Tang slips into the jacket, strolling through the streets until a fortuitous encounter with Prosecutor Ji. The sight of Ji ignites a primal urge within Tang, who promptly poses as his chauffeur. Soon, he has Ji bound and interrogates him about his sins. Roh Bin joins the scene, hacking into Ji's phone to uncover videos documenting the prosecutor's sexual assaults on women.
For Tang, this is undeniable proof. Without a hint of remorse, he plunges a blade into Ji, who drifts away lifeless. Together, they watch his body drift away, a grim testament to their twisted justice. Tang's confidence swells with each subsequent murder, his physical prowess growing to match his relentless pursuit of the wicked.
Meanwhile, Nan-gam and his team face a severe reprimand, leading to a physical altercation between Nan-gam's captain and their superiors. Both are subsequently dismissed. At the Chinese restaurant where Tang works, Detective Song Chon inquiries about Lee Tang, setting the stage for further developments in the gripping narrative of "A Killer Paradox," Episode 4.
