- Directors: David Dobkin
- Producers: Jackie Chan, Gary Barber, Roger Birnbaum
- Writers: Alfred Gough, Miles Millar
- Genres: Action, Adventure, Comedy, Western
- Actors: Jackie Chan, Owen Wilson, Fann Wong
The film opens in the Forbidden City in 1887, where Chon Lin (Fann Wong) is drinking tea with her father, the Keeper of the Imperial Seal of China. She tells him her brother, Chon Wang (Jackie Chan), is doing well as a sheriff in Carson City, Nevada, United States, but her father replies that her brother is dead to him. At that moment, Lord Nelson Rathbone (Aidan Gillen), leads a band of Boxers into the city, who attack the Keeper. Rathbone stabs him and leaves with the seal. As he lies dying, he gives Lin a puzzle box and a letter to Chon Wang.
Back in the Wild West, Chon Wang is doing well as sheriff, having captured an impressive array of fugitives. His deputy is relaxing with a book called “Roy O’Bannon Vs. The Mummy”, a highly fictionalized account of the events of the first film that now portrays Wang’s “Shanghai Kid” as a cowardly sidekick.
Wang receives a parcel, which contains the puzzle box and Lin’s letter, telling him his father is dead and that she has tracked the murderer to London.
Chon Wang travels to New York City to find his old partner Roy O’Bannon (Owen Wilson), needing his share of the gold left over from the first film to buy his ticket. Roy has left his brief stint in law enforcement, broken off his romance with Falling Leaves, spent most of the gold investing in the Zeppelin, and is now a hotel waiter and part-time gigolo. After they attempt prostitution to pay for a trip to England, the Mayor of New York arrives in search of his daughters, Roy’s latest clients. Chon Wang fights off a number of New York police officers, and he and Roy ship themselves to London in a crate. On the way, Wang tells Roy about his father, and Roy swears an oath to help reclaim the seal.
Roy and Wang are knighted, as is Artie, whose full name is now Sir Arthur Conan Doyle. Artie decides to become a writer, his stories revolving around his deductive reasoning technique, and asks Roy if he can use the “Sherlock Holmes” name. Roy and Lin kiss, and Roy proposes that he and Wang go to Hollywood to get in on the ground floor with motion pictures. They roll off in a buggy, with Charlie stowed away. Wang also manages to open the box his father sent him, finding a message inside reminding him of the importance of family.