As summer heats up, lychee fruit becomes one of the season's most sought-after treats. However, for people living in northern China during ancient times, it was a luxury, sometimes impossible to procure.

To demonstrate his love for Yang Yuhuan, the most famous concubine of the Tang Dynasty (618-907), Emperor Xuanzong ordered officials to transport lychees from Lingnan (a region encompassing Guangdong and Hainan provinces, the Guangxi Zhuang autonomous region, and parts of Yunnan and Fujian provinces) to Chang'an, the country's then capital, now Xi'an in Northwest China's Shaanxi province.

The journey spanned over 2,600 kilometers and took over 20 days on horseback, yet lychees only stayed fresh for three days.

How could the officials devise a feasible method to fulfill the emperor's seemingly absurd demand? Failure meant death. This life-or-death challenge fell upon Li Shande, the fictional "lychee envoy" in award-winning writer Ma Boyong's best-selling novella The Litchi Road.?