Although He Yongchao (Eddie) was born in a gangland area, he applied for the police academy after growing up and eventually graduated with excellent results to become a policeman. However, He Yongchao's first task after taking up his post was to be sent to the underworld as an undercover. He Yongchao hid his identity with extraordinary wisdom and courage, dealt with the enemy, provided a lot of important information to his boss, and was deeply trusted by his boss, but his girlfriend Afang, who did not understand all this, left He Yongchao with hatred. He Yongchao truly loves this career of fighting crime and is willing to sacrifice everything for it. However, when he saw his predecessor Yatai (Jin Xingxian) unfortunately died in the mission, He Yongchao's concept changed, and he wanted to return to a normal and safe life. The boss promised He Yongchao that he would be transferred back to the police force as long as he completed the last task.