Yiu Hok Sum is detective who is skilled in reading human body language, especially of people who try to deceive him. With his knowledge of criminal psychology, he is able to solve cases by paying close attention to the behavior and reactions of witnesses, with the help of his team. However, his relationship with his stepfather's side of the family is strained since his mother is looked down upon as a gold-digger, who married shortly after her Yiu Hok Sum, as a young child, witnessed the death of his father.