The 11th episode of Dear X resumes with the intense confrontation between Sung-hee and Ah-jin, which culminates in Sung-hee's face being slashed. Moon Do-hyuk arrives at the tail end of the melee, scoops up Ah-jin, and carries her away. Ah-jin awakens in the hospital, greeted by Jun-seo's tender kiss on her forehead.
Later, Do-hyuk calls Ah-jin to inform her that Sung-hee has been diagnosed with schizophrenia and is now confined in a psychiatric hospital. Ah-jin embarks on her laser treatment journey to heal the scar from the fight.
Jae-oh learns of these developments and delves into Sung-hee's story, who is now locked up in Haemil Psychiatric Hospital, the same facility where Do-hyuk's wife is admitted—though she's been missing for over a year. Meanwhile, Reporter Lim disappears after releasing a video detailing Ah-jin and Sung-hee's history from their school days.
As for Jun-seo, he appears content living with his mother. While out shopping with her, he encounters a producer named Han Ji-gyu. The producer strikes up a conversation with Jun-seo, revealing that the rumors surrounding Ah-jin and Sung-hee mirror the events in his first book—a chilling coincidence that adds another layer to the already intricate tale.
Surprised to learn that Ah-jin had been attacked by Sung-hee, Jun-seo reaches out to Jae-oh for verification, only to receive a disheartening response regarding their mysterious exclusion. As she rests at home, Ah-jin requests tea from the housekeeper, only to be abruptly interrupted by a hallucination of a maid approaching her with a knife—a vision that swiftly dissipates. Picking up her tea, she suddenly finds herself in possession of a glass of whiskey in an entirely different room. Emerging, she witnesses the maids diligently cleaning up a mess, while the doors to the third floor stand ajar and in disarray.
The housekeeper informs her that Ah-jin herself had created the chaos, both in the kitchen and on the third floor. A flashback reveals Ah-jin storming through various rooms until she comes across one filled with pictures of Do-hyuk and his ex-wife, prompting a fit of laughter.
In the present, the housekeeper inquires if she desires to visit the hospital, but Ah-jin assures her that she is not losing her sanity. Soon thereafter, Ah-jin returns to work. During the film shoot, she discovers Jae-oh waiting for her, claiming that she called him and mentioned Do-hyuk was causing her distress—a memory Ah-jin cannot recall.
With a deep-seated suspicion that Do-hyuk is the mastermind behind every misdeed, he also shares that upon investigating Sung-hee's background, he discovered that she had been boasting about her encounter with Do-hyuk just before she assaulted Ah-jin. Despite this overwhelming evidence, Ah-jin is hesitant to dissolve her marriage and lose all the hard work she's put in. Seeing her plight, Jae-oh offers to lend a helping hand.
However, fate takes a dark turn that night when Ah-jin experiences another hallucination, smashing a mirror in a fit of rage, resulting in cuts on her hands. In this moment of vulnerability, Do-hyuk appears, mending her wounds and reassuring her to lean on him as much as she needs.
Jun-seo encounters Jae-oh, who shares his suspicions about Do-hyuk's involvement. However, Jun-seo's skepticism towards Ah-jin's need for their assistance sparks an intense argument from Jae-oh.
During the film shoot, Ah-jin is shocked to learn of a sudden change in the script – a scene that eerily mirrors the one where she murdered her father with a bat. Struggling to perform the scene, she eventually goes too far, knocking out the other actor, who lands in critical condition. The tabloids are once again abuzz with talk about Ah-jin.
Later, when Ah-jin inquires about the added scene with the director, he reveals that it was insisted upon by Do-hyuk's company, Saturn, an investor in the film. Ah-jin confronts Do-hyuk about it, and he reveals his true intentions – he desires her complete dependence on him, but she resists. He claims his ex-wife was too fragile, but he knows Ah-jin will entertain him for a long time.
Furthermore, he shocks Ah-jin by revealing that it was him at the hospital earlier in the episode, not Jun-seo – Ah-jin was hallucinating. In her delirium, she even confided in him about her mother's death.
In the present moment, Do-hyuk tells her what she must do and without hesitation throws her into the pool.
He departs, reaching out to Jun-seo on the phone, instructing him to take care of Ah-jin. Jun-seo arrives by the swimming pool, where Ah-jin's anxiety mounts, claiming a desire to vanquish Do-hyuk and usurp his position. She returns home, utilizing her burner phone to contact Jae-oh. He reassures her, promising he has a plan and asks why he goes to such lengths for her. He confesses his delight in being by her side and being of service to her.
The narrative skips forward to Ah-jin waking up from an intravenous session, looking content and without a trace of memory from the film shoot incident. When she reunites with Do-hyuk, he notices that she has forgotten their previous conversation at the pool.
Meanwhile, Jae-oh confronts one of Do-hyuk's men, threatening retribution for the near-fatal incident. The man relays this news to Do-hyuk, who orders him to eliminate Jae-oh. Elsewhere, Jae-oh catches a glimpse of his brother in the distance and wishes him well.
That night, several cars arrive at Jae-oh's doorstep, unleashing Do-hyuk's men. Jae-oh escapes on his bike, sparking a chase that leads them all to the rooftop where Ah-jin had killed her father. In the ensuing melee, he is brutally beaten before ultimately being pushed off the side of the building.
Simultaneously, Ah-jin completes her final film scene, earning a round of applause from the assembled crowd.
