Episode 7 of "Buried Hearts" unfolds with the solemn rites of Sister Agnes' funeral serving as its poignant opening scene. Among the mourners stands Yeom Jang-seon, who assures Dong-ju that the truck driver responsible will be promptly apprehended. To their mutual astonishment, the truck driver is revealed to be Yang-chun, an underling of the Administrator, the very individual who, through Jang-seon's connections, had subjected Dong-ju to torture. Amidst the somber proceedings, a woman approaches Dong-ju, yet he fails to recognize her. Informed by an onlooker that she is Madame Pi, the woman who nurtured both Dong-ju and Sister Agnes, a veil of mystery deepens.
A poignant flashback transports us to Dong-ju and Hui-cheol's school days, where they find themselves summoned to the principal's office. Dong-ju had intervened in a brawl, aiming to shield younger students from Hui-cheol's aggression. Ironically, the blame for initiating the conflict falls upon Dong-ju. Hui-cheol's father's subsequent arrival only intensifies the situation as Dong-ju justly accuses him of bribing other students to frame him, with Jang-seon also present as a silent witness.
Another memory, eight years old, finds Jang-seon scrutinizing photographs of Dong-ju in his capacity at Daesan Energy. He murmurs about Dong-ju "tampering" with the company's accounting, hinting at a vendetta brewing within him.
In the present, Madame Pi confides in Dong-ju, revealing that his mother entrusted him and Sister Agnes to her care during their childhood. Overcome with emotion, she prompts Dong-ju to escort her to a quiet room, where Gu-ho discreetly follows. After a poignant conversation, Madame Pi bids Dong-ju rest until the mass commences.
Elsewhere, Il-nam dons a nurse's uniform, sneaking into the hospital with the stealth of a spy. He leads Yang-chun to a secluded room where Dong-ju awaits, poised for retribution. Yang-chun is soon tied up in the van's cargo area, while Dong-ju pedals furiously back to the church on his bicycle. At the church, Jang-seon and Gu-ho receive word of Yang-chun's plight, but Dong-ju's timely arrival for mass leaves them unsure of his involvement.
Later, Jang-seon convenes with a figure shrouded in darkness, who is revealed to be Assemblyman Nam Sang-cheol from Episode 1. The assemblyman whispers that "The Elder" seeks control over the patriotic fund. Jang-seon abruptly departs without a reply, leaving the scene ripe with intrigue. Meanwhile, Dong-ju emerges stealthily from a manhole, eavesdropping on the assemblyman's hushed conversation, adding another layer of complexity to the already tangled web of intrigue.
Jang-seon convenes with Il-do and lays bare their necessity to dispose of Daesan Energy. The Administrator reaches out to Gu-ho, instructing him to prod Jang-seon to locate Yang-chun. Meanwhile, Dong-ju persistently ignores Eun-nam's calls, engrossed in his own machinations. He sneaks into Chairman Cha's sanctuary, the safe, and begins surreptitiously filling it with soju bottles. Just as he finishes, the chairman enters, accompanied by Secretary Gong, and inquiries about a boy named Seong-hyeon, once brought home by Eun-nam's father. Secretary Gong feigns ignorance.
Upon their return, Deok-hui, Guk-hui, and Tae-yun catch sight of Ji Seon-u loitering outside their abode. He inquiries about Dong-ju, but Deok-hui deftly sends him away with a clever pretext. After Secretary Gong exits the chairman's office, Dong-ju reveals his presence to the chairman, with Il-do making a timely entrance. Dong-ju affects forgetfulness, pretending to recall only the safe's code. However, Il-do's sharp eyes catch Dong-ju concealing the soju bottle when Guk-hui enters.
Il-do informs the chairman that Yuseong Chemical is withdrawing from their deal with Daesan Chemical. Furthermore, Il-do divulges Jang-seon's desire to sell Daesan Energy, prompting the chairman to comprehend the urgency of paying Jang-seon to cease his disruptive schemes. Dong-ju plays along, "remembering" the chairman had concealed the safe's code within his pen stand. A fleeting flashback reveals Dong-ju earlier checking the pen stand, finding it empty, and then cleverly jotting down the codes on a fresh sheet of paper, placing it inside.
Dong-ju bears cash and gold to Jang-seon, who exhorts him to persist in retrieving his funds. Upon Dong-ju's departure, he inadvertently leaves Yang-chun's ring on the chair. Jang-seon and Gu-ho confront Dong-ju, who, in a daring move, seizes Gu-ho's gun and trains it on Jang-seon's head, maintaining his deceitful ignorance.
He even resorts to threatening his own life, leaving Jang-seon with no choice but to relent, acknowledging it all as a tragic misunderstanding. Dong-ju then retreats to the sanctuary of his home, finally allowing himself to mourn the loss of his beloved sister. Meanwhile, Hui-cheol and Eun-nam arrive at the Cha residence, bearing a selection of dishes from Eun-nam's in-laws as a gesture of goodwill.
Eun-nam, driven by concern, ventures to seek out Dong-ju, who greets her with a chill that mirrors the frost in his heart. He warns her that their paths, intertwined, only lead to sorrow and advises her to carve her own destiny. Yet, undeterred by his aloofness, she embraces him from behind, drawing a moment of tender vulnerability.
Just then, the piercing ring of Dong-ju's room phone interrupts the intimate tableau. The family soon gathers for dinner, a tableau of warmth and shared meals, with everyone present except Eun-nam, who promises to join them for dessert. As the dessert trays are presented, Secretary Gong mentions that the honey cookies, a gift from Eun-nam's in-laws, contain cinnamon—a subtle yet poignant reminder. Dong-ju, realizing this as Jang-seon's covert test to gauge his memory of his cinnamon allergy, deliberately consumes the cookies, defying the potential peril.
With heavy steps, Dong-ju makes his way to his chamber, but soon the grip of an unforeseen reaction takes hold. He chokes, his body convulsing in distress, and collapses to the ground. Frantic calls to emergency services echo through the air, but as Dong-ju lays in Eun-nam's arms, his life force slowly ebbs away, leaving a heart-wrenching cliffhanger at the conclusion of Buried Hearts Episode 7.
