In a fictional country inspired by imperial China, the story follows Maomao, a sharp-witted and poison-obsessed young woman who has been quietly training as an apothecary in the capital’s red-light district. Her life takes an abrupt turn when she is kidnapped by bandits and sold as a lowly indentured servant to the Imperial Palace, specifically the Rear Palace where the Emperor’s high-ranking consorts reside. Intent on keeping a low profile until her term of service ends, Maomao’s plans are foiled when she hears rumors of the Emperor’s infant heirs falling critically ill. Using her extensive knowledge of medicine and toxicology, she discreetly identifies the source of the sickness as poisoned face powder. Although she tries to remain anonymous, her deduction catches the attention of Jinshi, a strikingly beautiful and highly influential eunuch who oversees the Rear Palace.

Fascinated by Maomao’s immunity to his charms and her brilliant mind, Jinshi promotes her to a new position as a lady-in-waiting and poison tester for one of the Emperor’s favored consorts, the kind and pragmatic Gyokuyo of the Jade Pavilion. Despite her protests that she is “but a humble servant,” Maomao is repeatedly drawn into palace intrigue as Jinshi presents her with a series of increasingly complex medical and forensic puzzles. These range from proving that a purported double suicide was actually murder and uncovering a ghost story to be a case of carbon monoxide poisoning, to diagnosing a bizarre allergy and exposing a conspiracy involving ceremonial tool theft and attempted assassination.

Throughout the first season, the narrative deepens beyond episodic mysteries to reveal a layered political conspiracy. Maomao uncovers a plot targeting Jinshi orchestrated by a cunning court lady named Suirei, who uses her knowledge of herbal medicine to fake her own death and escape. The case forces Maomao to form an uneasy alliance with Lakan, a brilliant but face-blind military tactician who is later revealed to be her biological father, a secret tied to her own painful history at the Verdigris House brothel where her ill mother, Fengxian, once reigned as a top courtesan. Parallel to this, the series peels back the layers of Jinshi’s identity. While he is publicly known as a beautiful eunuch, it is gradually revealed that he is not a eunuch at all but is secretly the Emperor’s younger brother, hiding his lineage and taking anaphrodisiacs to serve in the Rear Palace for reasons tied to the former consort Ah-Duo. The season culminates with Maomao risking her life to save Jinshi from a falling pillar, resulting in a severe leg injury, and ends with the promise of further adventures as their complicated, slow-burning relationship deepens amidst the dangerous politics of the court.