Due to the debt left behind by his father, alpha Seo Taeyoon is at the mercy of Park Jae-in, a mob boss with a penchant for violence. But when Taeyoon is able to identify Jae-in as an omega by scent alone, the ruthless criminal is taken aback - because nobody should be able to smell his pheromones. Seeing this as his opportunity to regain what once was lost, Jae-in offers to pay off Taeyoon's father's loan in exchange for a life of servitude. Now Jae-in holds the key to both the physical and metaphorical locks around Taeyoon's neck. And so begins their relationship as master and slave...but there's no telling how it will end.