This is a legendary story about two western explorers. Although there are 100 years between them, they are destined to meet on the Great Wall. In 1908, as the first person to explore the Great Wall, American William Gallop recorded his 2800 kilometers of adventure with splendid pictures. However, he became unknown because he lost the adventure logs and pictures.. Today, William Lindesay, a British Great Wall researcher, found the log and photos of the old William's and started his adventure in terms of previous clues and his own 25 years' research experience. During two years, this young William traveled 35000 kilometers, and he tried to reveal the significant changes and the future of the Great Wall. This legendary story reveals the yesterday, today, and tomorrow of the Great Wall.