The Assassin is loosely based on the late 9th century martial arts story "Nie Yinniang" by Pei Xing, a core text in Chinese swordsmanship and wuxia fiction.[14][15]
The film is set in 8th century China during last years of the Tang Dynasty.[16][17] The film centers on Nie Yinniang (played by Shu Qi), an assassin who is directed to slay corrupt government officials by her master, Jiaxin, a nun who raised her from the age of ten. When Yinniang displays mercy by failing to kill during her duties, Jiaxin punishes her with a ruthless assignment designed to test Yinniang’s resolve: she is sent to the distant province/circuit of Weibo in northern China to kill its military governor Tian Ji'an — her cousin to whom she had once been betrothed.