The story tells about a former movie star in old Shanghai who was involved in a confusing murder case of eating melons. In order to prove her innocence, she joins hands with her personal assistant to find out the truth. The drama focuses on the two sisters with extremely different personalities and identities. Hu Xiaodie, who came from a grassroots background, was originally a female star who was over-packaged by commercialization; Hua Xiaoqing, who came from a well-off family, was originally an independent young woman who returned from studying abroad and her family fell into poverty. Because of the murder case, the whole city became a sensation overnight. In order to clear their suspicion, they began to learn the knowledge of investigation and reasoning skills by themselves, and eventually grew into real crime nemesis with the help of the patrol room.