Episode 13 of "The Tale of Lady Ok" kicks off with an intriguing twist as Kim So-hye's eyes widen in recognition, pointing at Tae-young and declaring her as the elusive Gu-deok. However, Tae-young, with a calm demeanor, brushes off the accusation and strides away, leaving a trail of confusion in her wake. Inside the premises, Scholar Cha hastily whisks Seung-hwi away as they uncover the startling truth about Nak-su's backing from Minister Bak, casting a dark shadow over their plans.
Concurrently, the moneylenders are on a relentless rampage, demanding repayment from those who took loans to purchase the mythical eternal ginseng. It transpires that Minister Bak orchestrated this ginseng scam through Nak-su, with the ultimate goal of securing the Magistrate's position.
Switching back to the Gu-deok saga, Tae-young is acutely aware that her departure would only solidify So-hye's suspicion. Similarly, Seung-hwi stands his ground, asserting that So-hye wouldn't remember his face among the crowd. The couple shares a hearty laugh, mocking their predicament while Man-seok looks on in disbelief, unable to fathom the absurdity unfolding before him.
Despite Tae-young's clever dissembling, So-hye remains unconvinced, insisting that Nak-su arrest her and force a confession. Nak-su, however, resists, his loyalty to his own doubts prevailing over So-hye's urgent pleas. Elsewhere, Scholar Cha, Hong, and Kim delve deeper into the scam, uncovering the startling revelation that So-hye is none other than Bak's concubine, and that Nak-su sold her to curry favor with the powerful minister.
As night descends, Tae-young encounters So-hye's slaves, and the truth unfolds like a grim tapestry. She confirms her identity as Gu-deok, her heart wrenching at the sight of their brutal torments, inflicted merely for aiding her escape. Yet, their unwavering loyalty shines through, as they profess no regrets for their actions.
The following day, Geumbok, the female slave, attempts to persuade So-hye to abandon her vendetta against Tae-young and return home. Her words fall on deaf ears, as So-hye remains resolute in her pursuit of truth and justice.
Into the entangling ginseng scam, Scholar Cha trembles at the prospect of confrontation, prompting Seung-hwi to deliver an identical bolstering speech. Together, they confront Nak-su, who remains as inflexible as steel. Seung-hwi, undeterred, warns him of impending legal action. Nak-su, cocksure of his ground in illegality, finds himself boasted back by Scholar Cha, who flaunts Tae-young's status as their legal eagle. Meanwhile, Hong offers a reluctant apology and seeks Tae-young's assistance.
Pooling their wisdom, Seung-hwi and Tae-young dive into the investigation. Tae-young engages in negotiations with the moneylenders to stave off the looming repayments, while Seung-hwi sets his sights on tracing the elusive eternal ginseng vendor, Heo Soon.
In a solo sleuthing endeavor, So-hye fans the flames of a rumor, branding Tae-young as Gu-deok. She ventures even to Madam Kim, who shields Tae-young with a veil of secrecy. Kim escalates her protection by threatening So-hye with legal repercussions, invoking Minister Bak's legitimate spouse and defamation charges against her for her father's misdemeanors.
Tae-young finds joy in Madam Kim's confession of delight in silencing So-hye's wickedness. Yet, Tae-young unveils the truth, prompting Madam Kim to urge her flight. But Tae-young is steadfast in her resolve to salvage the county, embracing the genuine Tae-young's dream as her penance. Madam Kim, moved, embraces her decision.
Perturbed by So-hye's actions, Seung-hwi hatches a clever plan. Dokki and Man-seok pose as Bak's bounty hunters, announcing the capture of Gu-deok. So-hye, duped, hastily departs for Hanyang.
In Hanyang, an enigmatic virus spreads its sinister wings. While probing this mystery, Do-gyeom brings the ginseng scam to the King's attention. Madam Kim's son, Deok-hun, is named Inspector General to probe the depths of the scandal. His father, impressed yet embarrassed, declines a return to his former glory. Deok-hun, torn between duty and worry, watches as Scholar Lee succumbs to the virus, convinced it's punishment for shielding Minister Bak.
Meanwhile, Minister Bak hoards every single medication potentially beneficial in treating the virus, intending to sell them at exorbitant, doubled prices. His fury intensifies upon discovering that Tae-young maneuvered Do-gyeom into alerting the King about the ginseng racket. In the midst of his irritation, So-hye arrives, inquiring about Gu-deok, a question that fuels his anger further. Bewildered, she throws a fit, prompting him to choke her in a fit of rage.
During his investigations, Tae-young uncovers another fraud operation in Jeolla. Meanwhile, to regain the goodwill of the county, Hong and his wife open their granaries to the starving populace. In solidarity, Tae-young also contributes supplies. Deok-hun arrives with a message from Provincial Governor Heo, revealing that Bak’s patron, the Left State Councillor, is undermining the nation through his insatiable greed, funded illegally by Bak. Deok-hun and Tae-young recognize that halting Bak is crucial to stopping the Councillor. Their quest begins by searching for evidence linking Bak to the scams.
That night, Madam Hong attempts to conceal jewelry for her son, Woong, earning a rebuke from Scholar Cha for her lack of conscience. Overwhelmed, Cha attempts to sever ties with her, but her tears and promises of improvement sway him into staying. Tae-young and Seung-hwi ponder additional ways to assist the county, their funds depleted. Seung-hwi remembers Man-seok's theater-days stash and attempts to pilfer it, but their plan is interrupted by Man-seok’s urgent news: Heo Soon is addicted to gambling. Cha and Seung-hwi devise a trap at Cheongsu’s largest gambling den.
As intended, Heo Soon falls into their trap, but Madam Hong bursts their bubble by revealing he is not the mastermind behind the eternal ginseng investment scheme. They realize someone impersonated Heo Soon, a revered physician, to deceive the county. Nak-su’s warning brings Minister Bak to the scene at the conclusion of Episode 13 of The Tale of Lady Ok. His forced smile fades as he lays eyes on Tae-young. Flashbacks haunt him of So-hye’s ravings about Tae-young and her deceit. He is astonishment to learn that the woman who has repeatedly foiled his plans is the very slave So-hye is searching for.
