The country boy in question is named "Kitty" (played by Jackie Chan), who moves to the city and becomes a dishwasher at a nightclub run by the gangster "Boss" (played by Bill Tung). Kitty is initially a low-ranking member of the gang, but after he buys some lucky roses from an old lady and uses them to win a game of mahjong, he becomes the new leader of the gang.
One of the nightclub's star performers is a singer named "Lily" (played by Anita Mui), who becomes Kitty's love interest. Kitty and Lily want to do a good deed for the old lady who sold Kitty the lucky roses, so they invite her daughter (played by Wu Ma) to visit from the countryside. However, the daughter is initially suspicious of Kitty's motives and thinks that he wants to sell her into prostitution.
Meanwhile, Boss has been causing trouble for a rival gang, who seek revenge by attacking the nightclub and abandoning explosives in the basement. A number of comedic and action-packed sequences ensue as Kitty, Lily, and the gang try to defuse the bombs and prevent the nightclub from being destroyed.
Eventually, Kitty and Lily are able to win over the old lady's daughter and help her start a new life in the city. The film ends with Kitty and Lily performing a song as the nightclub, now restored, reopens for business.