Tang Lin, a young journalist accompanies Zhang Gui, a war veteran, on a journey to return a fallen comrade’s belongings to his family, uncovering decades-old promises and gaining a profound understanding of the sacrifices behind the peace and happiness of today.

In the summer of 1917, Mao Zedong and his fellow student Xiao Zisheng, who were studying at Hunan First Normal University, embarked on a journey of poverty with only pen and ink, without a single word. Over the course of more than a month, they traveled to five places, measured the world with their footsteps, and felt the people with their hearts. In the process of opening up the "wordless book" of society, Mao Zedong gradually realized the location of the "great source" he explored day and night. This journey became an extremely important starting point in his life path.