Police officer Zhang Yiang, who had been away from front-line criminal investigation for several years, was sent to Sanjiangkou to investigate the case because of an anonymous report letter received by the provincial department.Not long after Zhang Yiang arrived at Sanjiangkou, he encountered the murder of the criminal police captain. While clearing his suspicion, he accidentally arrested the murderer of the serial murder case and quickly established his reputation.Subsequently, Zhang Yiang focused his investigation on local wealthy businessman Zhou Rong and his gang. However, thieves emerged one after another, and their intrigues triggered a series of butterfly effects, which instead helped Zhang Yiang lead the police team to achieve great successes.In the end, Zhang Yiang used his wisdom and courage to find out the cause of the murder of his colleagues and brought the real culprit to justice.