Orphan Song Yin (played by Julian Cheung) has been determined to be a policeman since he was a child. When he grew up, he successfully became a policeman and was about to be transferred to the important department of the police station, Oji, with excellent grades. Just before he joined Oji, his boss Huang Sir saw that he performed well and was a new face in Oji, so he selected him as an undercover agent to infiltrate the local underworld group Song Bo family. During Song Yin's undercover training, an accidental injury caused him to fall into a coma. In the coma, he recovered his memory of his previous life. It turned out that he was Wu Song, one of the heroes of Liangshan nine hundred years ago! After waking up, Song Yin found that he had mastered the acupuncture points of the human body for no reason, which further confirmed that he was Wu Song in his previous life. The undercover training was finally over, and Song Yin officially began his undercover operation. He successfully became the leader of the Song Bo family, Sha Dan, as a mainland immigrant, and took advantage of the Song Bo family and the other three underworld families to compete for territory with his skills and wits, and gradually gained Song Bo's trust. During this period, Song Yin observed the movements and figure of another colleague of O Ji, Zi Cong (played by Wang Xi), and recognized him as his brother in his previous life - Leopard Head Lin Chong. After repeated efforts, Song Yin finally made Zi Cong believe in him, and then the two of them joined forces to deal with the Song Bo family!