Belladonna, a count’s daughter, was systematically poisoned by her stepmother from childhood. Instead of dying, she developed a complete immunity to toxins and eventually acquired a taste for poisonous plants. Driven by this unusual resilience, she pursued botany with singular determination and became a respected plant scholar. Her peaceful life of research is shattered when a marriage proposal arrives from the Crown Prince, a man she has never met. Fearing that becoming a royal bride would end her scientific work, Belladonna hatches a desperate plan: she asks Will, a cheerful commoner she befriends at a local tavern, to help her lose her virginity so she can claim she is no longer fit to be a princess. On the day the Crown Prince is supposed to visit, Belladonna prepares to announce her “ruin,” but the man who appears before her is Will himself – he is the Crown Prince in disguise.

Will, whose full name is Prince Wilhelm, reveals that he too was repeatedly poisoned by his own uncle, Duke Vincent, who covets the throne. Recognizing Belladonna’s unique constitution and her knowledge of poisons, Will confides in her about the ongoing threat. What began as a farcical scheme to escape marriage becomes a dangerous alliance. Belladonna uses her poisonous expertise and resistance to uncover the uncle’s plots, protect Will, and expose the conspiracy within the royal court. Throughout the story, the two navigate political intrigue, assassination attempts, and their own growing romantic feelings. Belladonna’s bright, forward-thinking personality and Will’s genuine devotion drive the narrative as she learns to balance her love of science with the responsibilities of love and royalty. The story concludes with the couple overcoming the uncle’s schemes and securing the kingdom, with Belladonna ultimately embracing her place as the Crown Prince’s partner while continuing her botanical research.