Erna Hardy is the daughter of a ruined noble family, and she's a fish out of water among the elites of Lechen's high society. But this country bumpkin makes a giant splash when her official debut is interrupted by Prince Björn Dniester, the kingdom's "Royal Poisonous Mushroom." Suddenly, Erna is the hot topic on everyone's lips, and Prince Björn decides that courting the young lady will help him thwart persistent reconciliation attempts from his pining ex-wife. It's not until Erna unwittingly finds herself becoming a pawn in the prince's toxic game that she realizes how he's earned himself such a venomous title. And despite her best attempts to steer clear of his royal mess, an innocent mistake leaves her indebted to the prince indefinitely. Now, she's at his mercy as she works to pay off her debt. But is this royal mushroom really as deadly as everyone says?