In 1917, the First World War swept Europe, and at Princeton University in the United States, Wen Weijun, an international student from China, and Yasuo Yamamoto from Japan, both fell in love with a Japanese girl, Hideo Aoda. Graduation is approaching, facing choices, national interests are irreconcilable, and personal destiny cannot be chosen. In the struggle of painful contradictions, Ao Tian finally gave up the beloved Wen Weijun, and returned to Japan with Yasuo Yamamoto, and lost his love to Wen Weijun. But together with Lin Zhongqiang, Mao Zuhe, Chen Ke and other ambitious young people embarked on the road to return to China.

The world after World War I seems to be even more unstable. Japanese militarism is eyeing China, the National Revolution and the Northern Expedition are in full swing, and Western powers are trying to develop. The Second World War also spread arbitrarily on the land of China with the outbreak of the Songhu War. . In the changing international context, the Kuomintang and the Communist Party once again joined hands to determine the future of the nation, and the passionate young people who returned from studying in the United States also had their own different choices. Wen Weijun and Yasuo Yamamoto dreamed of becoming mathematicians, but their destiny was left They walked into the cipher front without gunpowder, and they had no choice but to be involved in this cruel war. Foreign classmates are like brothers, but they cannot get rid of the hatred of the country and the nation. They will be destined to become rivals of life and death. In order to protect his anti-war wife Hideo Aoda, Yasuo Yamamoto was forced to become a Japanese cryptographer. His fanatical propaganda of militarism caused his two daughters to take the initiative to participate in spy school and became cold-blooded killers. Yasuo Yamamoto was also killed. Tugged by the invisible hand, under the guidance of crazy militarism and the twists of love and hatred, it gradually fissioned, step by step involuntarily toward war.