On the final day of British rule in Hong Kong in late 1997, Detective Inspector Lee (Jackie Chan) of the Hong Kong police spearheads a raid at a shipping wharf, aiming to capture the elusive crime lord known as Juntao. Unfortunately, only Sang (Ken Leung), Juntao's right-hand man, is present, and he successfully manages to escape. Nevertheless, Lee triumphantly recovers numerous stolen Chinese cultural treasures that Juntao had taken, presenting them to his departing superiors: Chinese Consul Solon Han (Tzi Ma) and British Commander Thomas Griffin (Tom Wilkinson).
Soon after Han arrives in the United States to assume his new diplomatic role in Los Angeles, a shocking turn of events occurs when his daughter, Soo Yung, is kidnapped on her way to school by none other than Sang. In the aftermath of this distressing incident, the FBI alerts Consul Han, who promptly calls upon Lee for assistance in resolving the case.
Simultaneously, in Los Angeles, Detective James Carter (Chris Tucker) of the LAPD is working undercover at a doughnut shop, trying to make a deal with a man named Clive (Chris Penn), who is attempting to sell Carter some C4 explosives from his trunk. Just then, two police officers arrive, suspicious of the two men. As tensions escalate, Clive shoots at the officers and flees in his vehicle, with Carter pursuing him and successfully apprehending Clive after a chaotic chase.
Fearing negative publicity from a possible injury or death of Lee, the FBI assigns him to help the LAPD, with Captain Diel putting Carter on the case due to his previous reckless behavior during a mission. Carter, who had ambitions to join the FBI and is initially thrilled about the assignment, discovers that he is expected to keep Lee away from the investigation. Reluctantly, he agrees, but quickly devises a secret plan to solve the case himself.
Upon meeting Lee at the Los Angeles International Airport, Carter takes him on a sightseeing tour while simultaneously trying to gather intel from his underworld contacts. Lee eventually escapes Carter’s watch and heads straight to the Chinese Consulate, where an anxious Han and a team of FBI agents are eagerly awaiting news regarding Soo Yung's abduction. Amidst the chaos, Carter inadvertently communicates with one of the kidnappers (Sang), poorly arranging a ransom drop of $50 million.
At the ransom drop, Lee tries to alert the FBI that something is wrong, but his warning goes unheeded until a bomb detonates, killing several agents. After a brief chase, Sang escapes but drops a suspicious detonator. When they consult LAPD bomb expert Tania Johnson (Elizabeth Peña), they learn that it has the potential to trigger the C4 explosives. Carter and Lee decide to pay Clive a visit at the county jail, hoping to extract useful information. Clive, however, refuses to cooperate until Lee emphasizes the urgency of saving the young girl. Eventually, Clive reveals details about Juntao’s whereabouts at a restaurant in Chinatown.
At the restaurant, however, Carter is captured. Fortunately, Lee arrives just in time to rescue him, but they soon face the FBI’s frustration as they were blamed for ruining the ransom exchange. Soon after, Sang contacts Han and threatens to increase the ransom to $70 million, adding pressure to the situation. Despite being ordered off the case, both Lee and Carter are determined to save Soo Yung, leading to an unexpected partnership.
The climax of their adventure comes at a grand Chinese art exhibition at the Los Angeles Convention Center, where tensions rise as Carter, Lee, and Johnson infiltrate the event disguised as guests. Carter realizes that Griffin resembles a man he saw in Chinatown, and in an effort to create a diversion, he falsely alerts everyone about a bomb threat, causing panic and evacuations. Amidst the confusion, Lee discovers Sang handing Griffin a detonator, realizing that Griffin is, in fact, Juntao. The stakes escalate when Griffin threatens to detonate a bomb vest connected to Soo Yung if the ransom delivery is disrupted.
In the midst of the chaos, Carter finds Soo Yung and bravely removes her bomb vest, only to learn that it will detonate if not handled properly. Ultimately, in a desperate attempt, he drives a van into the building, placing the bomb vest in proximity to the crowd. As explosive confrontations unfold, Lee and Johnson join efforts to remove the vest from Soo Yung, while Carter throws himself into the fray, confronting Sang directly to save his partner.
As events come to a head, Lee and Griffin grapple for control, with explosive outcomes leading to Griffin’s downfall. In a shocking twist, Lee is left hanging from a rafter with the bomb vest, but Carter manages to catch him just in time. The film culminates with Han joyfully reuniting with Soo Yung, and in gratitude, sends Carter and Lee on a vacation to Hong Kong. Before their departure, Carter gets an unexpected job offer from the FBI, which he cheekily declines. The journey ends as Lee and Carter take off for Hong Kong, with Carter humorously showcasing his newly learned Chinese phrases, only to quickly request a new seat when Lee breaks into song.
