The sole son (Tony Leung Ka Fai) in a family of police officers marries Mina (Godenzi), an ambitious colleague only to incur the resentment of his four sisters, all policewomen, especially the eldest, Ling (Carina Lau). There is pressure on Tony to father a son, to keep the male line going, although Mina wants to delay pregnancy until she gets promoted to Superintendent. However, with a vicious Vietnamese gang on the loose in Hong Kong, Mina's crime fighting exploits place her in great danger...