The fifth episode of "Hyper Knife" kicks off with a tense scene where Deok-hee holds a knife against Myeong-jin's throat, allowing him to make one final phone call to his son. Upon completing the call, Deok-hee strikes, slashing Myeong-jin's throat, and then calmly hands him napkins to staunch the bleeding. Staggering out of the car, Myeong-jin reaches the precipice and plummets to his death, all while Deok-hee watches with a cold detachment.
The narrative shifts to a current conversation between Mrs. Ra and Deok-hee, with Myeong-jin's ring lying prominently on the table between them. Deok-hee demands an explanation, to which Mrs. Ra confesses that she had followed Deok-hee that fateful day and had managed to save Myeong-jin's life. However, the damage to his brain was severe, leading her to place him in a nursing home. She assures Deok-hee that he need not worry, as Myeong-jin passed away three months ago.
Elsewhere, Se-ok embarks on a hunting expedition, bringing down local boars with ruthless efficiency. Young-joo senses that something is troubling her, but Se-ok remains tight-lipped. When summoned to the police station, she proceeds to visit Ki-young at the hospital, where she unexpectedly encounters Deok-hee. He reveals to her that dog hair was discovered on the nurse's body and offers to assist her in evading the police if she performs surgery on him. She promptly refuses.
At the police station, Inspector Yang and his team investigate the mysterious disappearance of Detective Lee. Yang realizes that Deok-hee was the last person to call Lee. Meanwhile, Detective Seong meets with a shady figure in his car and informs him about Min, the clandestine surgery broker.
Yang confronts Deok-hee, who claims that Detective Lee had wanted to meet him that night but that he had canceled due to illness. Deok-hee adds that Lee intended to discuss Yang's alleged bribery. Yang's team reviews CCTV footage from Deok-hee's residence and confirms that he retired early that evening, adding another layer of intrigue to the unfolding mystery.
At Young-joo's earnest plea, Hyeon-ho pays Se-ok a visit. They together mourn over their current predicament, with Se-ok painting a vivid picture of her dream life—one immersed in the hallowed halls of the operating room, day in and day out. Hyeon-ho gently steers her toward realizing that Young-joo harbors deep concern for her wellbeing.
A nostalgic flashback unfolds, depicting Hyeon-ho escorting Se-ok to meet Young-joo, a man battling a colossal brain tumor yet resolute in his refusal of surgery. His inclination was towards a peaceful demise, but Se-ok harshly illustrates the alternative: a prolonged, agonizing end. She persuades him to undergo the surgery, reasoning that failure would at least grant him a swift release. Ultimately, Se-ok prevails.
In the present, Young-joo finds himself at the pharmacy when two figures enter, one of whom is the enigmatic individual who had previously crossed paths with Detective Seong. As dawn breaks, Se-ok notices Young-joo's absence and calls him, only to be told he's attending class. Later, he mentions plans for a movie outing, unbeknownst to her that he's actually being held captive in a basement by the same suspicious man. There, he's brutally beaten and interrogated about the nurse's murderer.
Se-ok ventures to the cinema, purchasing a ticket for herself. Mrs. Ra, tailing her discreetly, observes this and promptly informs Deok-hee, who is indulging in retail therapy at a department store. He responds by purchasing several cuts of meat, seemingly unperturbed by the developing drama.
Elsewhere, Inspector Yang obtains Min's contact information through one of his sources. Min reaches out to Deok-hee, hinting at an impending meeting with Yang and subtly suggesting his awareness of Se-ok's involvement. This revelation incenses Deok-hee, prompting an immediate call to Yang, who declines his request for a meeting.
The scene shifts to Deok-hee warmly greeting Min and his associate in a lavish apartment. He's prepared to broker a deal with Min to safeguard Se-ok, a proposition that piques Min's curiosity about their possible intimate history. The mere suggestion enrages Deok-hee, leaving Min puzzled by their complex relationship. Yang then calls Min to remind him of their appointment, but Min informs him of a change of heart. Telling Deok-hee he needs time to consider, Deok-hee reluctantly departs. Following this, Yang instructs someone to schedule the surgery, setting the stage for further twists and turns in this intricate narrative.
After the movie concluded, Se-ok was still at a loss to find Young-joo. Suddenly, her phone rang, displaying his number. The caller furnished her with an address, and upon arriving there, she witnessed Young-joo in a battered and bruised state. She was then escorted to confront the gangster she had once operated on during the premiere episode. He confessed his apprehension about the nurse's murder potentially implicating his associates. He instructed Se-ok to eliminate Min to ensure their collective safety.
As they headed back home, Se-ok posed the idea of relocating to the Philippines to Young-joo, who vehemently rejected it. Their argument was abruptly interrupted by the roaring passage of fire engines. Returning to her residence, Se-ok discovered her shed, where her beloved dogs rested, engulfed in flames. Mrs. Ra was present and could be seen calling Deok-hee, informing him that the deed was done.
Se-ok quickly dialed Deok-hee's number, insisting on a meeting. They agreed on a location, and with determination, Se-ok repeatedly rammed her car into Deok-hee's. Despite Deok-hee exiting and standing boldly between the two vehicles, Se-ok accelerated towards him but, at the eleventh hour, steered away.
Later, Min unexpectedly visited Se-ok's house, where Hyeon-ho and Young-joo were also present. Min announced a job for Se-ok, but she and Hyeon-ho flatly refused to collaborate with him. In retaliation, Min reminded Se-ok of their 120 million Won debt.
The cliffhanger of Hyper Knife Episode 5 saw the trio awaiting by a colossal ship, where Min's client's surgery was scheduled to take place. This intricate operation necessitated two surgeons, and to everyone's astonishment, the second surgeon revealed himself to be Deok-hee.
