Li Tsui-Ying (Pai Hung), the Best Secret Agent, disguises herself as a train conductor to assist Changjiang guerrilla leader Chiang Hsiao-Tien (Wu Chia-Chi) to evade the patrol of Japanese troops. Li adopts the pseudonym of White Peony in her Peking opera performance for the puppet government president, Han Zhaogui. Chiang discovers that his former lover Liu Feng has become Han's wife, but he finds that Liu still loves him and keeps their love token golden pheasant heart. White Peony would like to destroy the Japanese army’s project of building a secret airport. However, when she rescues Chiang from Han’s secretary, Ma Zuo-wen during an attack of Han in the cinema, White Peony falls in love with Chiang, without knowing that Chiang’s lover is Liu. In a final duel between White Peony vs Ma and Han, she realises how much Chiang loves Liu. She returns the golden pheasant heart that Ma took away from Liu to the lovers. The next day when Liu wakes up, White Peony has gone.

The film centres on a taxi driver who picks up a taciturn young girl with unsettling behaviour. What begins as a chance ride soon draws the driver and the mysterious stranger into a chain of events shrouded in doubt and suspicion, prompting audiences to reflect deeply on human nature, trust, and looming danger. Departing from conventional sentimental storytelling, the film adopts a suspense-driven narrative filled with twists. When the “suspect” gripping the steering wheel encounters a silent “enigma”, an accidental encounter becomes the light that pierces the darkest moments of their lives.