Sister Zheng (played by Zheng Yuling), a female police officer in Sichuan, is responsible for going to Hong Kong to capture escaped suspects and has to cooperate with the Hong Kong police. Police Chief Wu Weiguo (played by Tony Leung Ka Fai) is responsible for reception and cooperation in the investigation. He is confused by the naive and simple Sister Zheng and her assistant A Sheng (played by Zhang Jianting) who have arrived in Hong Kong for the first time.