In the port city of Jiangzhou, Wang Ruonan, the female deputy captain of the criminal investigation team of the Nancheng Branch, and undercover police officer Qiu Tian joined forces to solve the case, but they discovered the case of Liu Dong, the elder brother of Jiangzhou's black forces, who was hidden behind the case, suspected of drug trafficking. In order to solve the case, Qiu Tian, ​​who can return to the team, continued to go undercover alone, determined to destroy the Liu Dong Group. This action must be kept extremely confidential, and Wang Ruonan became Qiu Tian's only contact. Qiu Tian went undercover with Liu Dong's organization, experienced suspicion, and with his bravery and wit, gained Liu Dong's trust and became an important person in the organization. Qiu Tian was ordered to protect Li Feifei, an ex-girlfriend who was threatened by Liu Dong and knew her identity as a police officer, and her current husband, Zhou Zhiguo, a drug entrepreneur. Qiu Tian got the opportunity to participate in drug dealing, but the two consecutive arrests by the police were destroyed by internal and external factors, and Qiu Tian was almost exposed. At this time, the secret supplier behind Liu Dong surfaced. In order to find the source of the poison, Qiu Tian violated Wang Ruonan's order and took Liu Dong to abscond. Qiu Tian's gamble-style actions yielded an astonishing truth: it turned out that Zhou Zhiguo was the real mastermind behind the scenes. In the face of this major drug crime of collusion abroad, drug production and drug trafficking, Qiu Tian and Wang Ruonan worked together to cut off the source of evil in Jiangzhou.