On the last day of British rule of Hong Kong in 1997, Detective Inspector Lee of the Hong Kong Police Force leads a raid at the wharf, hoping to arrest the unidentified, anonymous crime lord Juntao. He finds only Sang, Juntao's right-hand man, who escapes. Lee recovers numerous Chinese cultural treasures stolen by Juntao, which he presents as a farewell victory to his departing superiors, Chinese Consul Solon Han and British Commander Thomas Griffin.
Shortly after Han takes up his new diplomatic post in Los Angeles, his daughter Soo Yung is kidnapped by Sang. Han calls in Lee to assist in the case, but the FBI, afraid Lee�s involvement could result in an international incident, pawn him off on the LAPD. Detective James Carter is tricked into �babysitting� Lee as punishment for botching a sting operation; when Carter discovers this, he decides to solve the case himself.
Carter takes Lee on a sightseeing tour, keeping him away from the embassy while contacting informants about the kidnapping. Lee makes his own way to the Chinese Consulate, where Han and the FBI await news about his daughter. While arguing with Agent-in-charge Warren Russ, Carter accidentally involves himself in a phone conversation with Sang, where he arranges a ransom drop of $50 million.
The FBI traces the call to a warehouse, where a team of agents are killed by plastic explosive. Spotting Sang nearby, Lee and Carter give chase but Sang escapes, dropping the detonator. Carter's colleague, LAPD bomb expert Tania Johnson, traces the detonator to Clive, a man previously arrested by Carter. Lee guilt-trips Clive into revealing his business relationship with Juntao whom he met at a restaurant in Chinatown, and earns Carter's trust. Carter goes to the restaurant alone and sees a surveillance video of Juntao carrying Soo Yung into a van. Lee arrives and saves Carter from Juntao's syndicate, but they are taken off the case after the FBI blames them for ruining the ransom drop, with Lee sent back to Hong Kong.
Carter appeals to Johnson for assistance and sneaks onboard Lee's plane, persuading him to help finish the case and stop Juntao. Griffin later involves himself in the case, revealing more about the HKPF's past with Juntao's syndicate, and implores Han to pay the ransom to avoid further bloodshed.
At the opening of a Chinese art exhibition at the Los Angeles Convention Center, overseen by Han and Griffin, the now $70 million ransom is delivered and Carter, Lee, and Johnson enter disguised as guests. Carter distracts the guests into leaving for their own safety, angering the FBI, but Lee catches Griffin accepting a remote for the detonator from Sang. Lee and Johnson conclude that Griffin is Juntao when Carter recognizes him from the Chinatown surveillance tape. Griffin threatens to detonate a bomb vest attached to Soo Yung, and demands the ransom be paid in full, as compensation for the priceless Chinese artifacts he preserved from Lee's raid. Carter manages to sneak out, locate Soo Yung in the van, and drive it into the building within range of Griffin, knowing that setting off the vest would kill him as well.
