In the distant future, a large portion of humanity lives on Mars, in cities that resemble those once found on Earth. The cities are protected from the inhospitable Martian atmosphere by dome-like force-fields. When a massive sandstorm breaks through the dome and destroys Mars New York, those in Mars Los Angeles must figure out how to stop the storm before it wipes them out next.
On holidays in Hong Kong, Mrs Ma gives birth to identical twins. A criminal in the same hospital attempts to escape, taking one of the twins hostage. The child is lost during the confusion, and Mr and Mrs Ma return to New York with one child. Years later, John Ma is a famous conductor and pianist, unaware that his twin brother "Boomer" is a mechanic/race car driver/bodyguard in Hong Kong. When John travels to Hong Kong to give a concert, the twins get caught up in each other's business, about which they are anything but experts.
A Hong Kong variation on Robin Hood. The corrupt officials of a Chinese village are continually robbed by a masked bandit know as "Iron Monkey" named after a benevolent deity. When all else fails, the Govenor forces a traveling physician (Donnie Yen) into finding the bandit. The arrival of an evil Shaolin monk, brings the Physician and Iron Monkey together to battle the corrupt government.