She calculated the odds of every game in London. She never counted on losing her heart to a scoundrel.Lady Charlotte Harbury has a secret. While other debutantes dream of waltzes, she dreams of probability equations. Desperate to test her theories, she commits the ultimate indiscretion: sneaking into a notorious gaming hell disguised as a man. She expects to find data. Instead, she finds disaster-and the one man she was warned to avoid.A Marquess with a dark past. Gabriel Ashcombe is London's most notorious rake, shielding a scarred heart behind a devil-may-care smile. When he discovers a brilliant woman in a borrowed coat amidst a card room brawl, he doesn't just see a scandal in the making-he sees a partner.A fake engagement to save them both. Caught in a compromising position, they are forced into a breathless charade: a betrothal to convince the ton they are madly in love. But their alliance is built on more than just saving face. Charlotte has uncovered a deadly conspiracy cheating the aristocracy out of their fortunes, and Gabriel is the only one who believes her.From glittering ballrooms to shadowed back alleys, their investigation draws them into a game where the stakes are life and death. But as the danger mounts, the lines between their pretend courtship and genuine passion begin to blur.Gabriel promised to protect her reputation. He never promised to protect his own heart. Themes: Fake Engagement, Fiercely Intelligent Heroine, Protective Hero, Regency Mystery, High-Stakes Intrigue, Slow-Burn Romance.