In 1977, Gu Beishan, a young educated youth stranded in a village in the Taihang Mountains without even a complete set of textbooks, sends a letter asking for help to the "future" in an old postal bag. In 2026, Su Jianwei, an industrial quality engineer whose career has hit a rough patch, receives the letter that has crossed forty-nine years. Starting with half a bar of soap and a few textbooks, the two gradually exchange technology, supplies, and personnel. Through education, production, entrepreneurship, and the reforms of the era, they change their own social standing and help people in both periods build better lives.
