The premiere of Hyper Knife kicks off with two doctors embarking on separate surgical journeys. Jeong Se-ok, a skilled surgeon, ventures into an operating room cleverly concealed behind the sanctity of a temple. She meticulously excises a tumor from the brain of Kim Doo-bong, a notorious gangster, amidst an intimidating presence of his henchmen. Her precision and calm demeanor underscore the gravity of the task.
In stark contrast, Choi Deok-hee, an elderly doctor, performs his surgery within the sterile confines of a hospital room. Upon concluding his procedure, he engages with a police sergeant probing into the realm of clandestine surgeries. The sergeant unveils a video depicting an exceptionally challenging brain surgery, asserting its near impossibility outside a hospital setting. Intrigued, the junior doctor inquires whether the dexterous hands in the footage could belong to Jeong Se-ok. Deok-hee promptly contacts a woman, tasking her with tracing the illegal surgery broker known as Min.
Within Se-ok's clandestine makeshift hospital, she awakens to check on her patient, who is fortunately recovering smoothly. A nurse who assisted in the surgery approaches her, revealing a surprising connection—they both once worked at Yeonshin University Hospital. Young-joo, Se-ok's junior, whispers that the nurse, hired by the gangsters, has a infamous reputation for mistreating elderly patients at another facility.
A tense moment unfolds as the nurse stealthily injects a suspicious liquid into the patient's IV. When Se-ok returns to change the dressing, she discovers him in a coma-like state. Seizing this opportunity, the nurse launches into a brazen extortion scheme, demanding money from Se-ok to keep her silence about her past misdeeds. Despite the dire situation, a cunning smile plays across Se-ok's lips as she reluctantly agrees to the nurse's demands.
Elsewhere, Deok-hee and Mrs. Ra confront the illicit surgery broker. He reveals that the Chinese had sent him the surgery video in search of the elusive surgeon, though he admits to having merely feigned interest, steering clear of brain surgeries. As Deok-hee and Mrs. Ra depart, a glimmer of conviction forms in Deok-hee's mind—he now suspects that Jeong Se-ok is indeed the surgeon captured in the video.
That evening, Deok-hee crosses paths with Inspector Yeom, a fellow townsfolk he knows well. Yeom extols Deok-hee's virtues endlessly, portraying him as the prodigy of their town who had triumphantly gained admission to medical school. Suddenly, Deok-hee is seized by a wave of discomfort and hastily dashes to the lavatory to administer medication.
Meanwhile, Kim Doo-bong's cronies are busy eradicating every trace of the clandestine surgery. He expresses his gratitude to Se-ok andpledges his assistance should she ever require it. The group subsequently departs, with Dr. Han, one of Se-ok's colleagues, volunteering to care for Kim for a brief spell. Se-ok, Young-joo, their anaesthesiologist, and the nurse find themselves the last souls lingering in the premises.
Se-ok instructs Young-joo to convey an icebox to Dr. Han, whom she reminds had inadvertently left it behind, cautioning him sternly against peering inside. She then urges the anaesthesiologist to seek some well-deserved rest. Unable to resist the allure of curiosity, Young-joo, on his way, pries open the icebox only to discover a meager assortment of snacks. Intrigued, he reverses the car's direction.
Back at the facility, the nurse partakes of water from Se-ok's bottle, only to faint momentarily thereafter. Upon awakening, sprawled on the floor, she realizes her bag is missing. Her frantic search leads her to the operating theater, where Se-ok ambushes her, encircling her neck with a wire in a chilling display of aggression. As Young-joo returns to the scene, he encounters Se-ok, who nonchalantly inquires about the location of a shovel.
Mrs. Ra presents Deok-hee with photographs capturing Se-ok's joyful moments playing amidst her Rottweilers, evoking a genuine smile from him. Observing this, Ra remarks on the striking resemblance between Deok-hee and Se-ok, planting a seed of contemplation in Deok-hee's mind about visiting her. Meanwhile, Se-ok has returned to her quaint pharmacy nestled in the town of Paju. As she exits her workplace, her eyes catch a glimpse of a man, adorned with an ankle monitor, fixated on her from the opposite side of the road. Unsettled, she shares this encounter with Young-joo upon reaching home.
Unexpectedly, her phone rings, and Deok-hee's voice announces his impending visit, sending shockwaves through her. Memories of a tumultuous past flash before her eyes – a scene where Deok-hee's actions led to her being ejected from the operating room. Fueled by rage, she lunges at him, her hands tightening around his neck, only to be restrained by fellow doctors. A resounding slap from Deok-hee follows, his words like a death sentence, denying her the chance to ever practice surgery again. She finds herself kneeling in the relentless downpour, pleading for mercy that remains ungranted.
In the present tense, Deok-hee arrives at Se-ok's doorstep. After exchanging pleasantries, he unveils a video of a brain surgery, commending her remarkable progress. Confessing his illness – a brainstem glioma – he places his trust in her hands, beseeching her to operate on him. Her anger flares as she questions his audacity, to which he coldly replies, hinting at the police's pursuit of her.
As Deok-hee prepares to leave, a sudden wave of pain washes over him. He fumbles with a vial of medication, but Se-ok, laughing maniacally, stamps her foot down, crushing it into shards. This chaotic tableau brings Hyper Knife Episode 1 to a dramatic close.
