Episode 3 of "Hyper Knife" kicks off with the arrival of Kim Myeong-jin and his son Ki-young at the hospital. Myeong-jin, an old friend and classmate of Choi Deok-hee, has come seeking treatment for a meningioma. Se-ok catches them sharing laughter and feels a twinge of suspicion.
Later, Se-ok gleans from a nurse named Ms. Na that Deok-hee is jittery about operating on his buddy. Her mood darkens further when she discovers that Deok-hee has chosen Ha U-yeong as his assistant, bypassing her. As the surgery commences, Se-ok dramatically interjects, claiming U-yeong's illness, and then "accidentally" slices Deok-hee's palm with a knife, seizing control of the operation.
The surgery concludes successfully, prompting Deok-hee to quiz Se-ok on her motives. She subtly hints that he harbored resentment towards Myeong-jin and intended to deliberately botch the surgery, explaining his preference for U-yeong over her. Se-ok insists she couldn't bear to tarnish his impeccable surgical record.
Meanwhile, Deok-hee stumbles upon Se-ok engaged in the hush-hush burial of Kwon Sin-gyu's body. His reaction to her grim task is curiously unperturbed. He queries her about the repercussions if her deeds were discovered and subsequently suggests she reconsider his offer to relocate to Boston. She categorically refuses to participate in his surgery.
The next morning, Sin-gyu's sister alerts the police to her brother's overnight disappearance. A cop cautions Se-ok, aware of Sin-gyu's persistent staring at her. Just when Se-ok rejoices over the news that her beloved diner is safe from being sold, her joy is swiftly dashed. Men from the Ministry of Health and Welfare descend upon her pharmacy, initiating an investigation that also encompasses Hyeon-ho's clinic. Consequently, Se-ok's pharmacy is suspended for 30 days, a clear maneuver orchestrated by Choi Deok-hee.
In a fit of rage, Se-ok phones Deok-hee, who informs her of his upcoming trip to Busan for the Ichida Awards.
Later, Young-joo discovers Se-ok confined within the confines of her car, her breath coming in ragged gasps as anxiety grips her tightly. He gently urges her to transport her mind back to a serene memory of unparalleled peace. The scene shifts to a poignant回忆 from the past, where Deok-hee, with a graceful sweep of his hand, brings Se-ok into his inner circle during a critical surgery, instructing her to scrutinize his every move with meticulous attention.
Young-joo and Se-ok find themselves in Busan, a city pulsating with life. In the bathroom's secluded alcove, Se-ok's ears catch snippets of conversation among a cluster of women, their whispers weaving a tale of Nanae Ichida, the awards' sponsor whose son, Haru, is battling a terminal illness. They decry the surgery as an uphill battle, nearly impossible to conquer.
As night descends upon the city, wrapping it in a shroud of darkness, Young-joo succumbs to the embrace of sleep. Se-ok, driven by an unyielding resolve, ventures out to confront Nanae Ichida in the privacy of her hotel room. Fluent in Japanese, her words flow like a silken river, reminding Nanae of their introduction by Deok-hee in the bustling metropolis of Tokyo.
With a flick of her wrist, Se-ok unveils a video, a testament to her surgical prowess—a young boy, battling both a tumor and haemophilia (the same affliction plaguing Nanae's cherished son, Haru), undergoing surgery with Se-ok's hands as both artist and healer. The video speaks volumes; a testament to her skill, as she navigates the delicate terrain without the slightest nick to a blood vessel. Se-ok extends her hand in a deal—her expertise to save Haru's life, in exchange for Nanae withholding the prestigious award for Best Surgeon from Deok-hee.
However, as dawn breaks, painting the sky with hues of pink and gold, Nanae remains steadfast, her resolve unbroken. She denounces Se-ok as a despicable soul, her heart unmoved by the plea. Nearby, Ha U-yeong catches a glimpse of Se-ok, storming away from Nanae's hotel room like a tempest in full fury. He attempts to intercept her, his voice a mere whisper in the wake of her intense emotion, but she ignores his call, disappearing into the crowd, leaving a wake of unspoken words and broken dreams.
Meanwhile, Deok-hee dispatches a surgical video to Alan, promptly following up with a phone call. Alan expresses his enthusiasm, revealing plans to arrive in South Korea within fortnight and considers it an immense honor to collaborate with "her." At one of Ichida's gatherings, Nanae approaches Deok-hee with circumspection, inquiring about Se-ok. Deok-hee heaps praises upon Se-ok, asserting that she has an impeccable track record. This revelation gives Nanae pause. Ultimately, she concedes to Se-ok's proposal, stipulating that the surgery must conclude within four hours at most.
Se-ok then contacts Hyeon-ho, instructing him to proceed to the airport. Under Nanae's direction, they are all transported to a hospital in Japan, where the surgery commences. The procedure progresses smoothly until an unexpected mishap occurs: Se-ok accidentally nicks a blood vessel, causing the patient to bleed profusely and uncontrollably.
Back in Busan, the Ichida Award is bestowed upon another physician, to the astonishment of all, excluding Choi Deok-hee. As Nanae and Se-ok enter the hall, Deok-hee grasps the gravity of the situation. Despite the earlier scare, the surgery proves successful, and Haru is very much alive!
Post-ceremony, Kim Ki-young recognizes Se-ok and approaches her, inquiring about his father. Sensing something amiss, Ki-young reveals that his father was recovering well until he mysteriously vanished one day. The police speculate that he might have run away.
Meanwhile, Deok-hee receives an urgent call from Inspector Yeom and Detective Lee Wan-il. They inform him that they have uncovered a lead concerning the illicit surgery video from Episode 1 and eagerly request his presence to view it. He readily agrees.
A fleeting memory resurfaces, recalling Nanae confiding in Deok-hee about Se-ok's proposition just before the awards ceremony. It was Deok-hee who urged Nanae to seize the opportunity presented by Se-ok. Presently, Se-ok confronts Deok-hee, accusing him of Myeong-jin's murder. She further alleges that his promise of sending her to Boston was a hollow gesture born out of vengeance, for she had intervened to save Myeong-jin that fateful day. Deok-hee brushes her accusations aside and strides away.
He subsequently rendezvouses with the detectives at the Buddhist temple where Se-ok had performed the controversial brain surgery. To their horror, the police team unearths the remains of the nurse whom Se-ok had brutally slain at the climax of Hyper Knife Episode 3, adding a chilling gravity to the already tense atmosphere.
