Manchuria, 1928. During the Japanese occupation of Shanghai, Itami, a young Japanese man, falls head-over-heels in love with Cynthia, a beautiful Chinese girl. However, an act of brutal violence by Japanese right-wing extremists will shatter Cynthia's world to pieces, bringing an abrupt end to their passionate relationship. Three long years later, as the hostilities continue to escalate, Cynthia, now going by the name of Ding Hui, has devoted herself to the cause, working as an operative for the underground resistance group known as the Purple Butterfly. But, sometimes, fate plays cruel games on people. Will Cynthia ever find out that her old flame, too, is in turbulent Shanghai, working as a secret agent bent on bringing down the Purple Butterfly?