Cha Seok-Hoon is a self-made man who rose from poverty only to face total ruin when a failed business venture leaves him with insurmountable debt. His wife, Na Hong-Joo, has spent her life sacrificing for him, but their devotion is pushed to the brink during a desperate trip to Hong Kong. There, they encounter Yoo Se-Young, a billionaire hotel heiress and workaholic “Woman of Iron" who views love as a meaningless distraction. Out of cynical curiosity, she offers Seok-Hoon a dangerous deal: she will pay off his life-destroying debt in exchange for three days of his time. Seok-Hoon takes the deal to save his future, but the choice creates an irreversible crack in his marriage. As the crisis of trust leads Seok-Hoon and Hong-Joo toward divorce, the cold Se-Young finds herself genuinely falling for the man she tried to break, while playboy and Se-Young’s family friend Kang Min-Woo complicates the fallout with his own predatory whims.