Park Cara is a rigid ruthless woman with double identity. To the world she's known as Park Rex, the southern mafia leader. A man with a stone-cold heart. Cara has kept her true identity as woman hidden. She was doing great until the mysterious nightcrawler, Byun Baekhyun became her personal bodyguard.      

Baekhyun is a heartless Mafia, so it seemed. He sees life differently, is always money-conscious, and never gives a damn about anyone but himself. Love is forbidden in his life after his previous experience until his driver accidentally knocked down a poor girl.

Lee Yumi was unfortunately sold to the most dangerous southern mafia boss Byun Baekhyun, but things took a drastic turn. For the sake of revenge and to save his reputation, Baekhyun forcefully got married to her. Little did he know that his heart will betray him.