In the 1960s, under the international situation of "dark clouds pressing down on the city and wanting to destroy it", Chairman Mao issued an order: good people and good horses go to the third line! Zhang Lijun, a descendant of a soldier, Ma Chaoyang, a son of a farmer, Lu Ruowen, a "capitalist daughter", and Xiang Qing, who returned from studying in the Soviet Union, and other young people full of fighting spirit and passion came to the mountains and ridges of the southwest, using their lives and youth to practice their ideals while performing a heart-wrenching love competition. Zhang Lijun has always admired Lu Ruowen, but because Lu Ruowen's comrade-in-arms and bestie Xiang Qing would not marry Zhang Lijun, she married Liang Yuqiang, who was attentive and thoughtful but shrewd. Just when Zhang Lijun slowly accepted Xiang Qing and was ready to get married, Xiang Qing died in an explosion. Liang Yuqiang divorced Lu Ruowen, who was "not born well", and Zhang Lijun and Lu Ruowen finally held their wedding after countless ups and downs. After the reform and opening up, Zhang Lijun served as the director of the military factory and Ma Chaoyang as the dean of the Aerospace Science and Technology Research Institute. Gao Zhanwu was diagnosed with stomach cancer, but he still stayed in the design room and workshop. Lu Ruowen, Ma Chaoyang, Zhang Lijun, Xiang Qing, Gao Zhanwu and others wrote a brilliant chapter in the construction of China's national defense industry in a barren mountain. They were fighters who dedicated their youth, love, life and their children to the Third Front, but they were as quiet as a valley that no one cared about.