Cynthia is a young Chinese woman in love with Itami, a Japanese man about to be sent home for military service. A devasted Cynthia moves back to Shanghai only to witness the death of her elder brother during an attack by the Japanese extreme right. She changes her name to Ding Hui and joins a secret resistance group code-named Purple Butterfly. This will be the same group that, years later, will plot to assassinate Itami.