Yudthapong is a businessman and widower who is facing bankruptcy, and owes money to Lin Lhan Sue (Tanin Manoonsilp), a Hong Kong Mafioso. Yudthapong promises Lin Lhan Sue that if he cannot pay off his debt, he will offer his eldest daughter, Nanthaka, to him. But when the time comes, he betrays Lin Lhan Sue and sends his second daughter, 17-year-old Ruthainak (Chalida Wijitwongthong), instead. When Ruthainak meets Lin Lhan Sue, she is attracted to him at the first sight, but she knows that she is just like an ugly duckling when compared to a beautiful swan like her older sister. Lin Lhan Sue is not pleased because he did not get what he was offered. However, Ruthainak is a strong and smart girl, and she does not hesitate to share her ideas with Lin Lhan Sue. She offers to pay off her father’s debt by working very hard. Time passes, Lin Lhan Sue notices her determination and talent, he starts to soften towards her. But being in a mafia business is full of dangers. One day, Lin Lhan Sue is attacked by another gang, but this young girl saves his life with her intelligence. Knowing that her life will be in danger if enemies finds out who she is, he sends out a news that ‘Cubic’, a secret code for his personal consultant who is a shadow behind his success is the one who saves his life. Other gangsters are now in search for ‘Cubic’. Will they succeed? While Lin Lhan Sue tries to find his true feeling about her, Ruthainak finds a secret to her life as well.