In early 1938, the Japanese army invaded the Shandong Peninsula. A box containing important military secrets of the Japanese army passed through Yidu County and was hijacked by the righteous Gongsun Xian. He was hunted down by Japanese spies. Before his death, he entrusted the box to Yang Baoguo, the owner of Yongxing Martial Arts Hall. Yang Baoguo swore to defend the box and was killed by Japanese spies. Yang Erhu, who was burdened with national hatred and family hatred, vowed to avenge his father and defend his country. Inspired by his brother, underground party member Yang Dalong, progressive students Xia Ling, Gongsun Yu and others, he gradually realized the weakness of his personal anti-Japanese power and that only the Communist Party could save China. Erhu inherited his father's will to fight against Japan and save the country and fought wits and courage with Colonel Okamura. He launched a desperate battle for the box and gradually uncovered the secret plan of the Japanese to develop highly toxic biological and chemical weapons. He finally thwarted the conspiracy of the Japanese army and successfully destroyed the Japanese army's biological and chemical weapons research and development base in Sheshan. Yang Erhu became more determined to defend his country and continued to grow on the road of resisting Japan and saving the country. He gloriously joined the Communist Party of China and became a true revolutionary fighter.