Kim Ji-won’s Doctor X has turned two mysterious letters into a question about medical ethics, professional arrogance, and the power doctors hold over unconscious patients.
Spoiler Warning: This article discusses Episode 4 of the 2026 Korean drama Doctor X: The Age of the White Mafia and theories about its upcoming episodes.
Two Letters That Changed Everything
A patient lies unconscious on an operating table. A surgeon opens his abdomen, expecting to treat a medical emergency.
Instead, she discovers something that should not be there.
Two letters.
D.N.
In Episode 4 of Doctor X: The Age of the White Mafia, Gye Su-jeong (Kim Ji-won) discovers a mysterious marking on the liver of Kwon Chung-hyun, a patient with a complicated connection to the newly arrived surgeon Na Dae-il (Jang Seung-jo).
It is the kind of cliffhanger that transforms a medical drama into a psychological thriller.
But the most disturbing part is not the mystery itself.
Something remarkably similar happened in a real operating room in Britain.
And that real-life case reveals why the letters D.N. may be more than a clue to one doctor’s past.
They may expose the difference between saving a patient’s life and believing that the patient’s body belongs to the person who saved it.
What Happened in Doctor X Episode 4?
Na Dae-il enters the hospital with an impressive reputation.
He is presented as a highly skilled surgeon with a military medical background. His professional achievements and seemingly considerate personality make him appear trustworthy.
His history with Kwon Chung-hyun strengthens that impression.
Years earlier, Kwon suffered severe injuries while serving in the military. Na reportedly performed an emergency operation that saved his life.
It sounds like the story of a heroic doctor.
Yet Episode 4 gradually changes how viewers interpret that story.
When Kwon returns as a patient, his connection to Na becomes increasingly unsettling. Gye Su-jeong eventually performs surgery and discovers the letters D.N. on his liver.
Na’s urgent reaction to the operation raises an obvious question.
Was he worried about the patient’s survival—or about something the surgery might reveal?
The episode does not conclusively establish who made the marking or why.
Nevertheless, it places Na’s carefully constructed reputation under suspicion.
And the initials invite one particularly provocative interpretation.
Does DN Mean Doctor Na?
One leading theory is that D.N. stands for Doctor Na, referring to Na Dae-il.
The theory is compelling because the patient previously underwent surgery associated with Na, and the doctor’s behavior suggests that he may fear the discovery of something from the past.
If the letters are a personal signature, they would imply something deeply troubling.
A surgeon might have left his mark on an unconscious patient’s organ.
But this is still a theory, not a confirmed revelation.
Other explanations remain possible, including a misleading clue or a medical abbreviation. The episode’s central achievement is making viewers question whether the doctor who once appeared to be a savior was telling the whole story.
The real-world parallel, however, makes the personal-signature theory especially disturbing.
The Real British Surgeon Who Branded His Initials on Patients’ Livers
In 2013, British transplant surgeon Simon Bramhall was working at Queen Elizabeth Hospital in Birmingham.
During two liver transplant operations, he used an argon beam coagulator—a surgical device ordinarily used to control bleeding—to mark the letters S.B. on patients’ transplanted livers.
The patients were under anesthesia.
They had not consented to having their organs marked with the surgeon’s initials.
The misconduct was discovered when another surgeon performed a subsequent operation and noticed the marking.
This was not a fictional television plot.
It became a criminal and professional disciplinary case in the United Kingdom.
In December 2017, Bramhall pleaded guilty to two counts of common assault. In January 2018, he received a community order and a £10,000 fine.
In 2022, he was removed from the UK medical register.
The disciplinary tribunal regarded his actions as a serious violation of the trust placed in medical professionals.
The case is particularly unsettling because it did not require an incompetent surgeon.
It involved a specialist entrusted with extraordinarily complex, life-saving procedures.
Technical brilliance did not prevent a profound violation of medical ethics.
That is the connection that makes the Doctor X cliffhanger so powerful.
Was the Real Surgeon Trying to Harm His Patients?
This distinction matters.
The documented British case does not establish that Bramhall intended to kill his patients or deliberately make them ill.
The markings were made during transplant procedures. Reports of the disciplinary proceedings described the misuse of a surgical instrument and the violation of patients’ bodily autonomy.
The tribunal did not need to establish a murderous motive to recognize the seriousness of the misconduct.
The problem was that a surgeon had used a vulnerable patient’s body for an unauthorized personal act.
The patient’s body became a surface on which the doctor expressed his own identity.
And that raises a question more disturbing than whether the letters caused physical injury.
Who gave the surgeon the right to do it?
The Operating Room Is a Place of Extraordinary Power
Most workplaces have some imbalance of authority.
A manager can direct an employee. A company can control access to resources. A senior professional can influence a junior colleague’s career.
But an operating room contains a more fundamental imbalance.
The patient may be unconscious, physically exposed, and completely dependent on the medical team.
The surgeon possesses knowledge, instruments, and immediate control over the patient’s body.
That authority is necessary for treatment.
Without it, many life-saving operations would be impossible.
Yet the same authority can become dangerous when a doctor begins to confuse professional responsibility with personal ownership.
A patient’s consent to surgery is not permission for everything a surgeon might wish to do.
A successful operation does not erase a violation of trust.
And saving someone’s life does not create a debt that allows the doctor to claim the patient’s body as a trophy.
This is where Doctor X becomes more than a story about a mysterious surgeon.
It asks what happens when professional authority is no longer restrained by ethical responsibility.
Na Dae-il’s Heroic Reputation May Be the Real Mystery
Episode 4 carefully constructs two images of Na Dae-il.
One is the celebrated surgeon.
He appears talented, composed, and capable of saving people in desperate circumstances.
The other is the increasingly suspicious figure whose past may contain something he does not want exposed.
The tension between these images is more interesting than a conventional good-doctor-versus-bad-doctor storyline.
What if the qualities that make someone appear heroic also make it harder for others to question them?
A doctor who saves a critically injured patient may receive admiration for years.
Colleagues may repeat the story.
Hospital administrators may use that reputation to strengthen their institution’s standing.
Patients may assume that exceptional skill guarantees exceptional character.
But those assumptions do not necessarily follow.
A doctor’s reputation is evidence of how others perceive the doctor—not proof that every action was ethical.
This is why Kwon Chung-hyun’s past matters.
His relationship with Na may contain the answer to the D.N. mystery. More importantly, it may reveal how a celebrated medical achievement can conceal a very different story.
Why Gye Su-jeong Is the Perfect Person to Discover DN
Gye Su-jeong’s defining characteristic is not simply her surgical ability.
It is her refusal to accept authority as a substitute for truth.
In a hospital shaped by hierarchy and institutional politics, she repeatedly challenges the assumption that seniority, reputation, or organizational power should determine what happens to a patient.
That makes her discovery of D.N. symbolically important.
The marking is hidden inside a patient’s body.
It cannot be explained away by a prestigious title, a public reputation, or a carefully rehearsed story about heroism.
It is physical evidence that demands an explanation.
The confrontation between Gye Su-jeong and Na Dae-il therefore represents something larger than professional rivalry.
It is a conflict between two possible understandings of medical authority.
In one, a surgeon’s exceptional skill becomes a source of personal power.
In the other, exceptional skill creates an even greater obligation to answer for one’s actions.
The better the doctor, the greater the responsibility—not the greater the privilege.
Did Doctor X Copy the Simon Bramhall Case?
The resemblance is striking.
Both stories involve mysterious letters appearing on a patient’s liver and a surgeon’s past becoming the subject of scrutiny.
The British case offers a clear real-world parallel for understanding the scene.
However, resemblance alone does not establish that the Korean drama’s writers officially based the storyline on Bramhall.
Without confirmation from the production team, it is more accurate to describe the case as a compelling parallel rather than a verified adaptation.
That distinction does not weaken the analysis.
It makes the real question sharper.
The disturbing possibility presented by Doctor X has already existed outside fiction.
Three Questions Episode 5 Must Answer
The next episode has several mysteries to resolve.
First: What does D.N. actually stand for?
If the letters represent Doctor Na, the marking could connect directly to Na Dae-il’s earlier operation. But the drama may still offer another explanation.
Second: What really happened during Kwon Chung-hyun’s military service?
The story of a heroic rescue is central to Na’s reputation. The circumstances surrounding the original injury and surgery may be more complicated than the hospital has been led to believe.
Third: What will the hospital do if the truth threatens one of its own doctors?
This may be the most important question.
Discovering wrongdoing is one thing.
Exposing it inside an institution that has invested authority and prestige in the accused professional is another.
And that is precisely the kind of conflict Doctor X was built to explore.
The Most Frightening Thing About DN Is Not the Letters
It would be easy to treat Episode 4 as a puzzle.
Guess the initials. Identify the suspect. Wait for the next episode to reveal the answer.
But the real-life liver-branding case gives the scene a deeper meaning.
A patient can survive surgery and still have their rights violated.
A surgeon can possess extraordinary skill and still abuse the trust placed in them.
And a hospital can celebrate a medical success while failing to ask uncomfortable questions about how that success was achieved.
The central issue is not whether a doctor is brilliant.
It is whether brilliance places someone above accountability.
A patient’s body is not a surgeon’s signature book.
That is the uncomfortable truth behind the two letters on Kwon Chung-hyun’s liver.
And if Doctor X follows that question to its conclusion, D.N. may become one of the drama’s most meaningful clues—not simply because it exposes one man, but because it challenges the power that allowed him to remain unquestioned.
What do you think D.N. means? Is it Doctor Na’s signature, a medical clue, or something more complicated? And if a surgeon saves a patient’s life but violates their trust, can that surgeon still be called a hero?
Sources and Further Reading
- The BMJ — Surgeon Who Put His Initials on Patients’ Livers Is Struck Off Medical Register
- The Guardian — Liver-Branding Transplant Surgeon Struck Off Medical Register
- CBS News — Doctor No Longer Allowed to Practice After Branding Patients’ Livers
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