Su-jeong takes over the ER, Dae-il can’t stop hovering, and the final seconds of Episode 4 turn a charming new surgeon into the creepiest man at GUMC.
Doctor X: Mafia in White Episode 4 (SBS and Netflix, starring Kim Ji-won as Gye Su-jeong) spends most of its runtime on Su-jeong’s new life in the emergency room and Dr. Na Dae-il’s very persistent attempts to charm her. Then it ends on a single image that rewrites everything we thought we knew about him. If you’re searching for the Doctor X Episode 4 recap, the ending explained, or just want to know whether the “DN” reveal is as unsettling as it sounds, you’re in the right place. Full spoilers ahead.
Doctor X Episode 4 Recap: A Demoted Surgeon, a Persistent Suitor, and One Very Bad Liver
A Flashback, a Frozen Contract, and a Furious Hee-sook
The episode opens in the past. Su-jeong pulls a young boy’s brother out of the burning White Wings Medical Corps building and tries to resuscitate the child. When she learns he didn’t make it, she breaks down in tears. It’s a quiet, heavy way to start, and it reminds us that the woman who looks so cold at GUMC is carrying a lot.
Back in the present, Director Bu tells Hee-sook and Su-jeong that her surgeon’s contract is on hold now that Dr. Na Dae-il has been hired. Hee-sook isn’t having it. She threatens to sue Director Bu unless he pays Su-jeong what he owes her, then takes Su-jeong out for a meal and wonders aloud why GUMC brought Dae-il in at all. Su-jeong’s answer is simple: he’s skilled after years of working in the military. Hee-sook is still furious that Su-jeong is being treated unfairly after she helped GUMC dodge a scandal with that complicated surgery. When she drops Su-jeong off at the hospital, she asks her to hold her head high, even though Su-jeong has been assigned to the ER.
Dae-il Joins the Team, and Su-jeong Takes Over the ER
Dr. Do, Dr. Bae and Seong-gyu give Dae-il a tour of GUMC, and he tries to introduce himself to Su-jeong. The doctors wave him off, insisting she’s far too uptight for small talk. Later that morning Dae-il visits his former teacher, Dr. Mun Yeong-jong, while Dr. Bae, Dr. Do and Dae-il discover Tae-kyeong passed out in his chair in the staff room. Tae-kyeong insists he’s fine and says he’s just rattled after assisting with a complicated surgery.
Then the ER gets its first real test. A tree falls on a group of people, five are injured, and a trauma patient comes rolling in. Su-jeong treats them one by one, and Seong-jin can’t help but be impressed. She also checks the MRI of a patient already in the operating room, decides to step into the surgery, and scoops out part of the patient’s liver. She hands the suturing to Dae-il, and the patient is saved.
Chairman Gu Squeezes Director Bu
While that’s happening, Chairman Dr. Gu sits down with Director Bu and Dr. Do to plan the press conference. He pins Jin-hyeong’s death on former GUMC Director Kim. Director Bu insists he did the right thing, but Dr. Gu threatens to cut off GUMC’s funding and reminds both men that he’s the one who sent Dae-il to the facility when they were short-staffed. It’s a cold little scene, and it makes clear who really holds the leash.
Coffee, Elevators, and a Whole Lot of Rejection
Dae-il tells Tae-kyeong that Su-jeong helped them during the surgery. He calls her “Snake Su-jeong,” which visibly bothers Tae-kyeong, and then admits he’s interested in her and asks Tae-kyeong to help him pursue her. In the ER, Seong-jin starts wondering whether Dae-il likes Su-jeong and grills her about what happened in the operating room. Dae-il turns up with coffee and desserts, hoping for some small talk, but Su-jeong won’t entertain him.
After her shift, Su-jeong clocks out and Dae-il follows. He finds her in the recovery room, looking at the first patient she’s officially credited with operating on. At home, Hee-sook’s friends Eung-gu and Mi-kyung chat about Dae-il’s interest in Su-jeong, and Hee-sook says he seems suspicious and wonders what he’s really after. Meanwhile, Tae-kyeong works late again and gets a nosebleed, thinking about Seong-gyu’s advice that he should finish his internship before moving to another department, since being a surgeon isn’t a rewarding position.
The next morning Dae-il tries to talk to Su-jeong in the elevator, and she simply shuts the door on him. The senior doctors step into the same elevator a floor later, and Su-jeong tells them the aneurysm didn’t rupture the way they’d predicted, mocking their doubts about her skills. I loved that moment.
Chung-hyeon Enters the Picture
That evening, Seong-jin convinces Su-jeong, Won-jin and Tae-kyeong to have dinner together. Outside the restaurant, Su-jeong spots a man, Kwon Chung-hyeon, collapsing, and takes him to the ER. Meanwhile, the surgeons have their own meal at GUMC, where they discuss Dr. Do’s collaboration with a pharmaceutical company owner and Dr. Mun’s drinking problem. When Dr. Mun walks past their table, Director Bu confronts him for working while reeking of alcohol, which upsets him. Dr. Do steps in to calm both men down.
In the ER, Seong-jin asks Chung-hyeon to undergo surgery. He tries to dodge the procedure, but Dr. Do, who is friends with him, arrives and insists on operating himself. Dae-il shows up too, and Chung-hyeon tells him he was planning to ask Dae-il to perform the surgery. He then recalls being bullied during his military service and explains how Dae-il saved his life.
The next day, Dr. Do, Dr. Bae, Seong-gyu and Tae-kyeong sing Dae-il’s praises, calling him a hero and blaming Su-jeong for disrespecting him. They also discuss Chung-hyeon’s decision to schedule his surgery a week out. Su-jeong studies his MRI and wonders whether he’ll even survive that long. As she leaves, Dae-il follows and asks her to share a meal. She says no and tells him Chung-hyeon’s condition is serious, asking him to check for a tumor. He compliments her surgical skills and confidence, but she walks away without a word. Tae-kyeong, watching the two of them, gets another nosebleed.
The Race Against the Clock
Over the week, Chung-hyeon gets worse. One day he collapses at the wheel while picking up plastic surgeon Dr. Jo Guk-jin’s son from coaching. The boy calls his father, who calls an ambulance, and Chung-hyeon is left behind in the car. Soon several emergency patients, Chung-hyeon among them, flood the ER.
Seong-jin calls Dae-il for help with Chung-hyeon’s surgery because they’re short-staffed. Dae-il says he’s busy and asks if someone else can do it. Seong-jin insists Su-jeong is the only one who can. With her access revoked, Su-jeong asks Tae-kyeong to help her get into the operating room, and she asks him and Won-jin to assist.
Seong-jin texts Dae-il to say Su-jeong is going ahead with the operation. Dae-il panics, abandons his dinner with Chairman Dr. Gu, and races to GUMC, but he can’t find Su-jeong anywhere.
The Ending: “DN” on the Liver
Su-jeong opens Chung-hyeon up and finds “DN” inscribed on his liver. That’s where the episode stops.
Doctor X Episode 4 Review: Su-jeong Shines, and Dae-il Gets Terrifying
My Take on the “DN” Reveal
That was a strange, unsettling way to end an episode, and I’m still chewing on it. Dae-il was the last person to operate on Chung-hyeon during their military days, so it’s hard not to wonder whether he really put his initials on a man he was treating. If that’s what happened, I’m honestly asking myself whether Dae-il is a psycho. All those compliments, the coffee, the dessert runs, and the friendly “hero” reputation suddenly feel like a mask.
He also seems obsessed with Su-jeong, and I’ll admit it was incredibly satisfying watching her shut him down again and again. The elevator door might be my favorite moment of the hour. My hope is that Su-jeong exposes Dae-il to Director Bu and the other senior doctors and he gets kicked out quickly, so she can get back to working as a surgeon at GUMC. I’m also really enjoying her bond with Seong-jin in the ER, and I’d love to see more of it.
What Works
- Su-jeong in the ER. Watching her treat five injured patients one by one, then step into a surgery and fix a liver, is exactly the kind of competence payoff this drama promises. Her demotion feels unfair, which makes every win hit harder.
- Dae-il’s charm-versus-creep tension. For most of the episode he plays the polite, persistent admirer. The final scene recasts all of it, and rewatching his earlier lines now gives them a different flavor.
- The elevator scene. Su-jeong shutting the door on Dae-il and then needling the senior doctors about the aneurysm is small, sharp and very satisfying.
- Seong-jin and Su-jeong’s chemistry. Their ER partnership is warm without being overplayed, and it gives Su-jeong a much-needed ally.
- The final image. A single two-letter inscription does more than a page of dialogue would.
What Doesn’t
- Too many side threads. Dr. Mun’s drinking, Dr. Do’s deal with a pharmaceutical company owner, Dr. Jo’s son, and Chairman Gu’s funding threat all appear in one hour. Some of them feel like set-up that never gets room to breathe.
- Dae-il’s “hero” reputation is told more than shown. The senior doctors call him a hero constantly, and Chung-hyeon’s military story supports it, but we never see much of it ourselves, which makes the reveal land with less contrast than it could have.
- Tae-kyeong’s nosebleeds. I like that the show keeps a quiet eye on him, but with only a couple of scenes it feels like a thread being held in reserve rather than developed.
- The cliffhanger leaves a lot unexplained. “DN” is a great hook, but the episode gives us no hint of what it means beyond the obvious, so it asks you to wait for next time.
Rating
8/10. A confident episode with a killer final shot. It loses a couple of points for crowding in subplots, but Su-jeong’s ER heroics and Dae-il’s chilling turn make it a really strong hour.
Doctor X: Mafia in White Episode 4 FAQ
Where can I watch Doctor X: Mafia in White? It airs on SBS in Korea every Friday and Saturday at 9:50 p.m. KST and streams on Netflix in supported regions.
How many episodes does Doctor X: Mafia in White have? The first season has 12 episodes. It premiered on October 9, 2026, with the finale scheduled for November 14, 2026.
What does “DN” on Chung-hyeon’s liver mean? The episode doesn’t spell it out. Given that Dae-il was the last surgeon to treat Chung-hyeon in the military, the initials point toward him, but we’ll need the next episode for confirmation.
Did Episode 4 do well in the ratings? Reports say Episode 4 reached 18.5% nationwide.
