They used test tubes to measure mountains and rivers, and used formulas to write love letters - chemists in war, idealists in life and death.
In 1937, the artillery fire at Marco Polo Bridge shattered the tranquility of the Peking Laboratory. Lu Qinghe, a talented chemistry student at Yenching University, left without saying goodbye and left a note to his junior sister Xia Shuying: "If the mountains and rivers are broken, how can we take care of our family?"
Three years later, in the occupied area of Shanghai, fate reunited them at a secret science and technology conference. He is a secret engineer of the National Government Resources Committee, working underground for the research and development of strategic materials; she is a young researcher at the Red Cross Pharmaceutical Factory, saving lives in the pharmaceutical workshop. As the war approached, he asked her: "You can't turn back once you step on this road. Are you sure you want to follow me?"
