On the eve of the July 7 Incident, the young Chinese Hendler (Eddie Peng) traveled across the ocean from the United States and returned to Peking, where he had been away for more than ten years, to practice medicine. However, his real name is Li Tianran. When he was thirteen years old, he witnessed his master's family being killed by his senior brother Zhu Qianlong (Liao Fan) and the Japanese Ichiro Nemoto (Kenya Sawada). Tianran, who escaped by chance, was sent to the other side of the ocean by American Dr. Hendler and received extremely rigorous training. Now he has set foot on his homeland with a top-secret mission. Hendler and his son rented the house of the mysterious man Lan Qingfeng (Jiang Wen), who was a participant in the Xinhai Revolution. He was very close to Zhu Qianlong, the current police chief, but he secretly encouraged Zhu to get rid of Ichiro Nemoto by killing Li Tianran. Li Tianran, who was eager for revenge, found his enemy, and Dr. Hendler tried his best to stop his adopted son from taking risks. In this process, socialite Tang Fengyi (Xu Qing) and tailor Guan Qiaohong (Zhou Yun) were also involved in the whirlpool of men's intrigue. Until the July 7 Incident broke out, all the contradictions ushered in the moment of determination... This film is adapted from Zhang Beihai's novel "Hidden Heroes".