Set in Joseon-era Korea, Lady Cho (Son Ye-jin), a high-ranking noblewoman trapped by Confucian social restrictions, uses covert psychological manipulation to exert control over her surroundings. She strikes a covert agreement and wager with her cousin and former lover, Cho Won (Ji Chang-wook), a infamous aristocratic libertine. Lady Cho tasks Cho Won with seducing Ahn Hui-yeon (Nana), a chaste young widow who has devoted herself to mourning. As Cho Won executes his targeted campaign of seduction, genuine emotion destabilizes their calculated game, sparking dangerous betrayals, illicit affairs, and tragic social consequences across the elite community.