Kim Hye-in found herself receiving an unsolicited nude video from Min Yoo-hee, while Lee Eun-rang, in pursuit of Park Woo-jin, discovered his deceit; he had retired for the night, abandoning his promised rendezvous with Black Dog. Desperate to reach Kim Hye-in, Lee Eun-rang dialed her number only to find it constantly engaged.
In a state of panic, Kim Hye-in dashed to Min Yoo-hee's doorstep, yearning for a face-to-face confrontation. Instead, she was met with a cryptic text urging contemplation on how she might aid Min Yoo-hee. This threat cowed Kim Hye-in, rendering her a mere pawn in Min Yoo-hee's scheme. Surveying the opulent surroundings, she felt powerless to resist or alter her fate. Desolation took her to the streets, where, peering into the vast, murky depths of a river, suicidal thoughts crept in.
Elsewhere, Min Ryul-hee dressed with exhilaration, her mood abruptly dashed by her mother's reminder. Fuming, she picked up her phone to find that Baek Jina's drug scandal had been closed without suspicion. Park Woo-jin, cast aside by her, now sought to reconcile, aiming to stabilize his company's collaborations. Min Ryul-hee seethed with rage, her nemesis acquitted while she teetered on the brink of being entangled once more by her deceitful partner. The announcement of Baek Jina's clearance set off a chain of reactions, compelling those involved—Cha Jin-wook, Baek's parents, and others—to recalibrate their interests, origins, and strategies. Joy mingled with sorrow as Baek Jina triumphantly returned to school, only to notice Kim Hye-in's absence. Messages went unanswered.
Baek Jin-na inquired of Cha Jin-wook if he had orchestrated her exoneration, to which he offered neither confirmation nor denial, instead querying her plans. She intended to uncover evidence of Min Yoo-hee's role in pushing Kim Hae-in down the stairs, utilizing the Black Dog channel to eradicate Min Yoo-hee entirely. In a heartfelt confession to Seo Do-yeon, Kim Hae-in expressed her desire to bring an end to everything, apologizing for exploiting his affections. She further revealed Min Yoo-hee as the one who had pushed her.
That evening, the chairman of the board hosted a dinner with Baek Jin-na and Cha Jin-wook's father, proposing that their engagement ceremony coincide with Cheongdam International High School's 30th anniversary celebrations—a suggestion met with eager agreement.Park Woo-jin asks Min Yool-hee if she's been taking good care of Oh Shi-eun's phone and tells her about the invitation Black Dog sent him. Min Yool-hee is furious. Black Dog's message indicates someone saw Park Woo-jin taking Oh Shi-eun's phone and scolds him for not even doing such a small thing. Comparing this to Cha Jin-wook, Min Yool-hee finds Park Woo-jin increasingly unsightly. With a series of thoughts building up, Min Yool-hee threatens to keep her family informed of their breakup by threatening to reveal the video of Park Woo-jin having sex with someone else. Min Yool-hee also shrewdly wonders if Park Woo-jin's preoccupation with Oh Shi-eun's phone might be a hidden secret, and she shifts the blame, blaming Park Woo-jin for pushing Kim Hae-in down the stairs.
Park Woo-jin inquiries of Min Yool-hee if she has diligently attended to Oh Shi-eun's phone, simultaneously informing her of the invitation dispatched to him by Black Dog. Min Yool-hee's fury ignited instantaneously. Black Dog's message, which suggested a witness had observed Park Woo-jin handling Oh Shi-eun's phone, reprimanded him for neglecting such a menial task. When juxtaposed with Cha Jin-wook, Min Yool-hee found Park Woo-jin's demeanor increasingly unsavory. As her thoughts escalated, Min Yool-hee menacingly threatens to inform Park Woo-jin's family of their separation by exposing a compromising video of him engaging in intimate relations with another individual. Suspecting that Park Woo-jin's fascination with Oh Shi-eun's phone might harbor a concealed secret, Min Yool-hee deftly shifts the blame onto him, accusing him of shoving Kim Hae-in down the stairs.
Confronted with Min Yool-hee's relentless onslaught of accusations, Park Woo-jin plunged into a profound depression, unable to articulate any words of reconciliation. A video from the Black Dog channel was unleashed, revealing the murderer to be concealed within the Diamond Six. Upon witnessing the news, everyone speculated about the killer's identity, leaving Kim Hye-in astounded, as only a select few were privy to this information. She pondered who Black Dog could be and how he had obtained the secret she had assiduously guarded.
Recalling the time and venue Park Woo-jin had imparted to her regarding Black Dog's rendezvous the previous night, Min Yool-hee scrutinized the surveillance footage. To her astonishment, she discerned Kim Hye-in masquerading as Black Dog during that period, filling her with indignation.
The chairman's office was enveloped in palpable tension. Black Dog's persistent video expositions had tarnished the school's reputation. Despite the elapsed time, Black Dog's identity remained shrouded in mystery, with the repercussions lingering. Even if a scapegoat were identified, the Black Dog incident still needed to be addressed. Kim Hye-in observed Min Yool-hee demanding the deletion of the video. However, after reviewing the surveillance footage, she presumed Kim Hye-in to be Black Dog and insisted she relinquish it to the chairman. Despite Kim Hye-in's warnings, Min Yool-hee stood firm and demanded that Kim Hye-in identify Baek Jina at her engagement ceremony as the perpetrator who had shoved Kim Hae-in.
Kim Hye-in found herself ensnared in an incessant dilemma as Min Yool-hee's menacing text messages resumed. Cha Jin-wook revealed his true identity as Black Dog to Baek Jin-na. With no outlet for his fury, Park Woo-jin sought out Kim Hae-in, informing her that it was due to her actions that Min Yool-hee had terminated their engagement. He viciously assaulted Kim Hae-in, who initially resisted but eventually succumbed. Meeting Kim Hye-in in a state of despair, Kim Hae-in implored her for assistance and begged her to end it all. Upon witnessing her injuries, Kim Hye-in wept inconsolably, informing her that the necklace was no longer in her possession. The final glimmer of hope extinguished, Kim Hae-in wandered helplessly towards the speeding truck on the road.
