The fourth episode of Dear X commences with the poignant moment where Jung-ho lays a lethal blow upon Sun-gyu with a bat. In the ensuing minutes, Sun-gyu succumbs to his injuries, and Jung-ho vanishes into thin air. Ah-jin seizes the beanie, shreds it into pieces, and flushes the remnants down the drain. At the hospital, she concocts a tale to the police, accusing Jung-ho of her father's murder. At the station, Jung-ho unearths a startling revelation: that her father was wearing the beige beanie associated with Ah-jin's stalker. However, Ah-jin maintains a blank on the beanie's existence.
A flashback interlude depicts Jung-ho's frantic attempt to summon an ambulance after the assault. It is during this fleeting moment that Ah-jin reveals her startling truth - that he is her father. She urges him to retreat home, assuring him she will seek aid herself. The present narrative reveals Ah-jin overhearing the detectives' nefarious plot to absolve Jung-ho's guilt and shield his impending baseball comeback. She seizes a photograph of the lead detective accepting a bribe from someone connected to Jung-ho's agency. The detective, prying into Ah-jin's abode, discovers fibers from the beanie adrift in her toilet. Soon, she finds herself at the police station as a suspect.
There, the detective unveils the beanie's tale and discloses the discovery of two more bludgeoning incidents on Sun-gyu's head. Ah-jin utilizes a fleeting moment alone with a female officer to request a review of her phone's recordings. The female officer complies, uncovering a clip of other detectives conspiring to pin the blame on Ah-jin. The matter escalates to internal affairs but yields no concrete evidence. The lead detective now vows to pin Ah-jin down.
A representative from Longstar Entertainment pays Ah-jin a visit, offering assistance with strings attached, of course. Meanwhile, the police uncover more about the stalker, uncovering footage of him with Ah-jin at a convenience store. Joon-seo, undeterred by the mounting evidence, confesses to stalking Ah-jin and even admits to wanting to eliminate Sun-gyu, who he deems a monster. He details his plan to drug Sun-gyu with sleeping pills and bring him down at his motel; when absent, he resorted to using the baseball bat to take Sun-gyu down while Ah-jin was unconscious. As a result of this confession, Ah-jin is finally cleared to leave.
A haunting flashback revealed that after flushing the beanie, Ah-jin's mind was haunted by the ghostly voice of Sun-gyu, leading her to strike him again. Joon-seo arrived on the scene, shocked to find Sun-gyu lifeless and the beanie lodged in the toilet. He gathered the pieces, stuffed them into a garbage bag, and tossed them outside, then erased Ah-jin's fingerprints from the bat, using it to deliver a fatal blow to Sun-gyu once more. As a final act, he journeyed to Sun-gyu's motel room and planted the sleeping pills as proof of his presence. However, the police discovered evidence that Joon-seo had visited the motel after Ah-jin's home, not before. Regardless, the detectives charged Jung-ho with the crime and whisked him away. Joon-seo and Ah-jin walked free, unscathed.
All this unraveled as a scheme orchestrated by Mi-ri, who had convinced Ah-jin to sign with her. But Mi-ri had a condition: she asked Ah-jin to stay away from Joon-seo. Her plan was to make Ah-jin famous and powerful, but she feared that once Ah-jin achieved success, these incidents would resurface. She believed it was best for Ah-jin and Joon-seo to stay apart. Later, the case files were sent to Mi-ri, who kept them in a safe place.
Despite Mi-ri's counsel, Ah-jin met with Joon-seo. Joon-seo called her out for manipulating Jung-ho and threatened her for her sins. Despite this, he insisted on staying by her side. Ah-jin told him firmly that she would not see him again and left.
Over time, Ah-jin blossomed into a highly successful actress. The episode ended with Jung-ho watching one of her films from his prison cell, reflecting on the twisted events that had unfolded.
