Episode 12 of "Buried Hearts" kicks off with a harrowing car crash that claimed the lives of Sun-ho and Gyeong-won. Il-do, though injured, manages to stumble out onto the road, a sole survivor amidst the wreckage. A stunning revelation unfolds as it becomes clear that the individual who handed Il-do the DNA test report prior to the fatal accident was none other than the enigmatic Administrator.
During a session with hypnotherapist Kang I-hyeon, Dong-ju's suppressed memories of the accident resurface with startling clarity, revealing Il-do as the one who steered their vehicle off the road. An unexpected twist occurs when Kang Seong, returning home, stumbles upon a recording of Dong-ju's hypnotic session on I-hyeon's laptop. I-hyeon, seemingly skeptical, suggests that Dong-ju's accusation against Il-do might stem from a misunderstanding.
In the sanctuary of his home, Il-do is haunted by a dream where young Seong-hyeon morphs into Dong-ju. Awakening abruptly, he finds Dong-ju sitting ominously before him. Dong-ju produces an article detailing the accident and, unmasking his true identity, issues Il-do an ultimatum: flee Daesan with Deok-hui and Tae-yun, or face certain death at his hands.
Il-do's mind drifts back to a cherished memory of giving Gyeong-won a floral hair tie during their youth. The same hair tie adorned little Seong-hyeon and now rests in Dong-ju's possession. Haunted by these connections, Il-do places a call to Jang-seon, requesting a firearm.
Determined to shield Eun-nam from the harrowing truth, Dong-ju presents her with the newspaper article as tangible proof of Il-do's innocence in her father's demise. Elsewhere, Won-bae relentlessly pursues information about the Dandelion files from the Administrator and Yang-chun. Yang-chun, dropping subtle hints, mentions one of the Administrator's buildings, suggesting that the basement might harbor untold secrets.
Later, we uncover that Tae-yun overheard Dong-ju's confidential discussion with Il-do. Desperate to mend fences, Eun-nam presents Deok-hui with the photograph bestowed upon her by Dong-ju, only to have Deok-hui fly into a rage and berate her. Seeking clarification, Eun-nam ventures to Kang Seong, who assures her that nothing romantic transpired between Sun-ho and Gyeong-won, emphasizing that the child was not Sun-ho's offspring. They were merely comrades, united in their days as student activists. When Eun-nam mentions Dong-ju possessing the hardcopy of the photo, Kang Seong's memory is jogged, realizing he had given it to young Seong-hyeon. Meanwhile, Il-do confides in Jang-seon, who concurs that Dong-ju must be eliminated.
Elsewhere, Dong-ju and Won-bae escort Yang-chun to the Administrator's edifice. Yang-chun guides them to two bulky safes, only to discover they are barren. While they explore, Gu-ho and his henchmen encounter the Administrator. Upon Dong-ju and Won-bae's return, they find him gravely wounded. However, Dong-ju stumbles upon a map inscribed within one of the Administrator's tomes, directing them straight to the Dandelion files. They entrust these files to Tae-geum, who agrees to decipher them.
The big day for Ji Yeong-su and Chairman Cha's nuptials arrive, but the chairman experiences another memory blackout. Jang-seon convinces the chairman to proceed with the ceremony nonetheless. Post-wedding, amidst the familial reunion, Secretary Gong reveals to Deok-hui that Seong-hyeon is still alive. Simultaneously, Gu-ho hands Il-do a firearm. Kang Seong's repeated calls go unanswered.
Returning home, Dong-ju discovers a package awaiting him. Inside lies a DNA test result comparing Il-do and Dong-ju, undeniably proving their kinship. Additionally, Dong-ju receives a transcription from Tae-geum of Jang-seon's conversation, further confirming that Dong-ju is Il-do's son, not Sun-ho's.
Just then, Il-do dials Dong-ju's number, jogging his memory about their scheduled encounter that evening, where Il-do intended to "present his side of the story." As Dong-ju arrives at the designated meeting spot, Il-do takes aim and fires a shot at him. At the eleventh hour, Jang-seon interrupts over the phone, revealing to Il-do that Dong-ju is, in fact, his son. Dong-ju collapses but quickly regains his composure, sitting up with a laugh. In a moment brimming with irony and emotion, he dares his father to finish what he started, uttering these words at the cliffhanger of Buried Hearts Episode 12.
