Twelve years have passed since Chief Inspector Lee and Detective James Carter helped Chinese Ambassador Solon Han and his daughter Soo-Yung, by discovering and saving Geneviève in Paris (Rush Hour 3). Lee is now retired, still unmarried, and resides in Hong Kong. He is living a very quite and sad lifestyle in a one-bedroom apartment in downtown. Carter is the current Lead Detective at the central LAPD office in Los Angeles. He is divorced and is raising his teenage son. A run-of-the-mill drug bust goes wrong once Detective Carter overhears an important conversation. The Hong Kong based cocaine drug lord, Tato Xylang, who is in control of the drug movement, is the biological brother of Sang (Rush Hour 1 antagonist). Carter is caught easy dropping on the drug villains. Xylang comes to realize that Carter is one of the detectives who is reasonable for the death of his brother. Carter is chased and is forced to hide out overnight. During the chase, Carter loses his wallet; Xyland and his gang finds the wallet and uses his drivers license to confirm his identify and locate his home. Xyland and his gang kidnaps Carter's son. Xyland blackmails Carter into helping him move his drugs on the dock. If he is successful in helping, and keeping the LAPD out of the area, then he will get his son back. Carter becomes frantic and goes to the only person he can trust. Carter arrives in Hong Kong to find a washed-up and aged Inspector Lee. After explaining his situation, Lee agrees to help Carter get his son back. Carter puts Lee through a "Rocky" parody training seminar, and then the two return to the States to go to war.
