Cynthia and Itami are young lovers in the pre-Sino Japanese war time in Shanghai. Itami is called home to Japan for military service, leaving Cynthia behind in her homeland. After Cynthia's brother is killed by a pro-Japanese protestor she joins the Purple Butterfly resistance movement. As time passes she is again reunited with Itami, but this time they are on opposite sides. She is assigned to help kill his boss. He is hunting down the Purple Butterfly members.

This movie utilizes tight shots often through blue lenses. More often than not the scenes are smoky or rainy, shot with a shaky hand. There is a scarcity of dialogue. The scenes will either feel intimate or claustrophobic, and sometimes they can feel both. Purple Butterfly can be maddeningly hard to follow at times as the story bounces back and forth in time and between characters, but buried under the pretty wrapping are solid performances by Zhang Ziyi, Nakamura Toru, and Feng Yuan Zheng. The sadness and inevitability of the war to come lingers over the story like the smoke and rain enveloping each scene.