Chen Zilong (played by Donnie Yen) is a skilled undercover agent who has been embedded in the underworld for many years. As the right-hand man of gang leader Long Mao Xiong (played by Zho Zhaolong), he is under immense pressure, especially as the leader has begun to doubt him and has threatened the life of Zilong's mother (played by Bao QijIng). Zilong desperately wants to be reinstated and withdraw from the underworld. This time, Brother Xiong sends Zilong to the mainland to investigate the true intentions of an organization member, Sunny (played by An Zhijie). Sunny, who hails from Chinatown in the United States, used to run in the same circles as Zilong in his early years, but as he grew in power, he secretly began to take Xiong's goods. Meanwhile, Zilong's superior, Zhang Sir (played by Zheng Zhongji), demands that Zilong investigate Sunny in exchange for his reinstatement. However, the trip to the mainland turns out to be fraught with danger, as Sunny proves to be cunning and ruthless, and there are frequent conflicts in coordination with the local police. In addition, a mysterious assassin known as 'Blade' (played by Zhang Hanyu) appears and disappears, pulling Zilong into a web of deepening conspiracies.
