Episode 12 of "Hunter with a Scalpel" kicks off with a nostalgic flashback. Choi Min-guk and young Se-eun return from a clandestine mission, with him issuing her tasks to cleanse the van before his departure. However, her curiosity leads her to her bedroom, where she's delighted to find birthday decorations and a cake thoughtfully arranged by Eun-seo. Additionally, there lies a brand-new school uniform, personalized with her name. Amidst her joy in unwrapping her presents, Eun-seo ventures into the van, her expression turning to sheer horror upon discovering pools of blood within.
In the present timeline, Se-hyun's hand is a gruesome sight, swathed in bandages. At the police precinct, Kwon Hyung-jo bursts in, recounting how a man assaulted him and was subsequently knocked out by a woman who then stitched his wounds, instructing him to stay hidden for a week. He mentions the assailant's peculiar scent of laxatives.
Chang-jin shares this with Jung-hyun, and they deduce that Choi Min-guk is behind the assault. Chang-jin attempts to persuade his superiors to probe Choi Min-guk, but the police chief, irritated, transfers him to the traffic division. Undeterred, Chang-jin informs his teammates of his collaboration with Jung-hyun. However, the other two officers insist on joining the investigation.
The trio converges at Jung-hyun's laundry shop, where they embark on an investigation. Inside, they uncover a room adorned like a little girl's sanctuary, realizing that Choi has meticulously wiped away all fingerprints. Just as Choi Min-guk enters the scene, Seok-woo cleverly distracts him to allow his colleagues to slip away, but Choi soon realizes their intrusion.
Inside Choi's van, Se-hyun notices Se-eun wearing her watch, which she reveals has an SOS button and instructs her on how to recharge it. Exhausted from blood loss, Se-hyun faints. Later, Choi arrives at the van and resumes their journey.
Seok-woo figures out that Choi rented a car, prompting Chang-jin to leverage his access to CCTV footage to pinpoint their location. Jung-hyun speeds off in pursuit, eventually spotting both the car and the van along an isolated stretch of land. As he witnesses the van driving away, Jung-hyun gives chase. Choi halts the van and sends Se-eun off to procure medication, but she returns empty-handed, explaining that she needs a prescription.
The trio heads to the pharmacy in unison, their steps leading them to procure some much-needed medication. Seizing the moment, Se-hyun sneaks a can of pepper spray from the shelves and lunges at her father with it. Swiftly, he halts her assault, delivering a forceful blow as Jung-hyun, sensing the danger, rushes to intervene. Tragically, Choi draws a knife and plunges it into Jung-hyun, felling him to the ground. Yet, Jung-hyun's valiant effort to grapple with Choi buys just enough time for the wail of sirens to pierce the air, signaling the arrival of the police.
Officers train their guns on Choi, the tension thick enough to cut with a knife. But Choi, ever cunning, seizes Se-eun as a human shield and makes a daring escape behind the wheel of a nearby vehicle. As Jung-hyun's life ebbs away, his words are tinged with regret as he apologizes for doubting Se-hyun, his voice fading into the silence before he slips into unconsciousness.
