Restricted to an abandoned mansion on the outskirts of London in fulfillment of a promise to her father, lonely Cardia lives day to day isolated from the world. Her body carries a deadly poison that rots or melts anything her skin touches, prompting the locals to call her a “monster.” Her last conversation with her father two years ago, telling her to stay out of sight and never fall in love, is the furthest back she can remember. One day, her quiet solitude is interrupted as the Royal Guards break in to capture her. It is then that Cardia meets Arsène Lupin, a chivalrous thief, who helps her escape the soldiers’ clutches. She soon finds herself on a journey with Lupin to locate her father, who holds the answers to her mysterious condition.