Episode 2 of "Mary Kills People" kicks off with So-jeong, Ye-na, and Dae-hyun sealing their partnership, as So-jeong lays down her stringent criteria for selecting clients: affirmation of untreatability by at least three doctors, unbearable physical incapacitation, and the futility of painkillers.
The narrative then shifts to a pivotal moment where Woo-mi collapses mid-performance on stage, a ballet dancer's dream shattered. Rushed to the hospital under So-jeong's watchful eye, Woo-mi awakens to confess her theft and consumption of Bavron, pleading with So-jeong to keep her secret lest her mother exile her overseas.
Elsewhere, detectives delve into the backgrounds of their suspects. Ye-na, scarred by her father's abandonment and her twin brother's prolonged illness, found solace and camaraderie with So-jeong in the hospital corridors, while financial burdens from medical expenses have saddled her with debts. Dae-hyun, meanwhile, served time for a medical mishap that brought him into contact with Kim Si-hyun.
Ye-na brings So-jeong's attention to a potential new client, Cha Soo-yeon, a high schooler diagnosed with terminal colon cancer, his time on earth numbered. Abandoned by his mother post-divorce and solely supported by his father, Soo-yeon fears the excruciating pain predicted by his doctor in his remaining weeks. So-jeong hesitates, torn between compassion and concern over Soo-yeon's youth and the gravity of his decision. She tasks Dae-hyun with locating Soo-yeon's estranged mother, Lee Ji-young.
Simultaneously, police interrogate Choi Kang-yoon's wife regarding So-jeong, uncovering an autopsy report that reveals Bavron was not the culprit in Kang-yoon's demise; instead, asphyxiation claimed his life, a method outside So-jeong's repertoire.
In a parallel narrative thread, Kim Si-hyun receives an unexpected visit from Gu Gwang-chul, his enigmatic superior. Suspecting Dae-hyun's true intentions with Bavron, Gwang-chul issues a stark warning to Si-hyun: cease all dealings with Dae-hyun immediately.
So-jeong visits a welfare hospital managed by Father Yang, the clergyman whose path she crossed at the climax of episode one. There, fate leads her to encounter Hyun-woo, who, in the twilight of his life, is in the process of donating his possessions. Lending a hand to an ailing patient and contributing generously to the hospital, So-jeong discovers that Father Yang is no stranger to Hyun-woo; they are old friends, albeit unbeknownst to the priest that his companion's end is near. So-jeong has securely stored the Bavron within a locked cupboard at the hospital, occasionally checking on it, only to find Hyun-woo sitting on the stairs, his vision blurred by impending demise. As she gently assists him, Hyun-woo inquires about her motivations for such selfless endeavors, to which she replies, desiring to empower individuals with the agency to decide between life and death.
Later, So-jeong and Dae-hyun convene with Soo-yeon, whose demeanor suggests an urgent embrace of mortality. Despite asserting a lack of regrets, Soo-yeon mentions a girl he holds dear, prompting Dae-hyun to vow to facilitate his confession of affection before his final moments. Hyun-woo then invites So-jeong to the orphanage that was his childhood home, situated in the vicinity where he once lived with his parents. He proposes spending his remaining days in an apartment nearby, a poignant full circle for his final chapter.
Meanwhile, Soo-yeon and Dae-hyun eagerly await Hye-young, the object of Soo-yeon's affections, emerging from her late-night studies. Amidst their conversation, Soo-yeon playfully accuses Dae-hyun of harboring feelings for So-jeong. Hye-young finally appears, but Soo-yeon's condition suddenly worsens, compelling Dae-hyun to escort him back home, their encounter abruptly cut short by fate's cruel hand.
During dinner, So-jeong comments on Hyun-woo's unyielding will to survive, evident from his relentless pursuit of various treatments. However, it was the consecutive failures of these therapies that eventually extinguished his desire to live. Determined, So-jeong reaches out to one of Hyun-woo's former physicians, inquiring about any recent breakthroughs in treatment. The doctor, soon after, calls her back with exciting news of a novel clinical trial in the United States.
Brimming with optimism, So-jeong rushes to Hyun-woo's side, intent on sharing this beacon of hope. Yet, Hyun-woo feels insulted by the suggestion of undergoing yet another battery of tests, prompting him to demand that she pull over. He declares his intent to sever ties with her and exits the vehicle abruptly.
Subsequently, Hyun-woo ignores So-jeong's calls. Worried, she embarks on a search, discovering that he has abandoned his job at the delivery service and that his apartment stands empty. A visit to a nearby pharmacy reveals he has purchased a significant quantity of painkillers, raising alarm bells. Meanwhile, Hyun-woo finds himself paused at a stall selling hair clips, contemplating buying one as a gesture for So-jeong.
Driven by concern, So-jeong visits Father Yang's hospital, this time confessing that her friend is battling a brain tumor. Shortly after, a violent husband of one of Father Yang's patients bursts in, waving a knife and causing a commotion. As So-jeong finds herself in imminent danger, Hyun-woo arrives just in time to incapacitate the assailant.
Once the man is apprehended by the police, So-jeong apologizes to Hyun-woo for her earlier handling of the situation. He then presents her with the hair clips he had considered buying and wonders if he still falls short of her expectations. She assures him that he does not, but insists that she wants him to fight on. Suddenly, Hyun-woo leans in and kisses her, sealing the moment with an unexpected gesture.
The second episode of "Mary Kills People" concludes with a detective on the hunt for Hyun-woo, leaving viewers to ponder: Could Hyun-woo possibly be affiliated with the police?
