In the 1930s, Hong Kong was in turmoil and gangs were everywhere. Hong Kong tycoon Hu Lao Tou found private detective Ai Yao (played by George Lam) and asked him to investigate Mrs. Hu because he felt that Mrs. Hu had been acting strangely these days. After investigating, Ai Yao found out that it was the bad priest Kabang (played by Michael Hui) who had hooked up with Mrs. Hu and wanted to steal Hu Lao Tou's priceless stocks. After their plan was discovered by Ai Yao, he chased Ai Yao everywhere. When Ai Yao was on the run, he found out that Hu Lao Tou was not a Hong Kong tycoon, but just a con man. His purpose in coming to Hong Kong was to cheat money from gangsters like Kabang. Hu Lao Tou invited Ai Yao to join him and set up a trap to cheat Kabang. After discussing with his good friend Inspector Robin (played by Teddy Robin), Ai Yao decided to use the same trick against him.