Lin Jianwei, an intern doctor, unexpectedly travels back in time because of an old register and receives a mysterious mission to find her great-great-grandmother. While searching for clues, she becomes a medical orderly with the help of Red Army soldier Chen Xinghuo and uses her modern medical knowledge to treat the wounded. Along the way, she witnesses the flames of war, life and death, and painful farewells, while being deeply moved by Chen Xinghuo and the soldiers' unwavering faith. From an outsider intent only on finding her way home, Lin gradually chooses to face danger alongside them. She comes to understand that history may not be changed, but there will always be people who choose to advance through the gunfire. The answer she has desperately sought also begins to emerge along the banks of the Xiang River.