Shanghai, 1942. The World War II Japanese occupation of this Chinese city continues in force. Mrs. Mak, a woman of sophistication and means, walks into a café, places a call, and then sits and waits. She remembers how her story began several years earlier, in 1938 China. She is not in fact Mrs. Mak, but shy Wong Chia Chi (Tang Wei). With WWII underway, Wong has been left behind by her father, who has escaped to England. As a freshman at university, she meets fellow student Kuang Yu Min (Wang Leehom). Kuang has started a drama society to shore up patriotism. As the theater troupe's new leading lady, Wong realizes that she has found her calling, able to move and inspire audiences -- and Kang. He convenes a core group of students to carry out a radical and ambitious plan to assassinate a top Japanese collaborator, Mr. Yee (Tony Leung). Each student has a part to play; Wong will be Mrs. Mak, who will gain Yee's trust by befriending his wife (Joan Chen) and then draw the man into an affair. Wong transforms herself utterly inside and out, and the scenario proceeds as scripted -- until an unexpected fatal twist spurs her to flee.

Three years later, with no end in sight for the occupation, Wong, having emigrated to Hong Kong, goes through the motions of her existence. Much to her surprise, Kuang re-enters her life. Now part of the organized resistance, he enlists her to again become Mrs. Mak in a revival of the plot to kill Yee, who as head of the collaborationist secret service has become even more a key part of the puppet government. As Wong reprises her earlier role, and is drawn ever closer to her dangerous prey, she finds her very identity being pushed to the limit...