In Hong Kong, American businessman Paul Wagner, his wife Katherine Wagner, and their 6 month old twin sons Chad and Alex are watching a parade. When the parade ends, Paul and his business partner Nigel Griffith, who run Griffith-Wagner Enterprises, step up to a podium and dedicate the Victoria Harbour Tunnel, which is an underwater tunnel that connects Hong Kong Island to the mainland. That night, Paul, Katherine, and the twins are on their way home when Paul notices a carload of Chinese men following them. Paul uses his CB radio to alert his friend Frank Avery to the situation. Paul and Katherine arrive home with the twins a few minutes later, and see that waiting for them is a gang of Chinese men led by a musclebound assassin named Moon. Moon and his men shoot both Paul and Katherine dead, and plan to kill the twins -- until Frank shows up and kills all of Moon's henchmen, but Frank gets shot while Moon escapes. Chad and Alex end up separated. 25 years later, Chad is a martial arts expert and aerobics trainer in Los Angeles. Frank raised Chad in Paris, France after the murders. Frank talks Chad into going to Hong Kong with him. Frank has decided that it's time to get the twins together and get revenge, and reclaim what's rightfully theirs. They board an airplane to Hong Kong. Hours later, they arrive in Hong Kong. On that night, they go to a Mah Jongg Parlor and go inside. Chad is approached by a blond haired woman who obviously thinks he's someone else, then a man who looks like Chad knocks Chad out cold. The man is Alex, and the woman is Alex's fiancee Danielle Wilde, who thought Chad was Alex. She, Chad, and Alex are all surprised to be told by Frank that Chad and Alex are brothers. Alex and Danielle have a hard time believing it. Frank explains that Paul supervised the construction of the Victoria Harbour Tunnel. Halfway into the project, Paul encountered financial problems, so he pulled in Nigel Griffith as an equity partner. Nigel got his money from a secret loan, courtesy of Hong Kong drug kingpin Raymond Zhang. When the tunnel was completed, and Paul's expertise was no longer needed, Nigel and Raymond had Paul and Katherine murdered by Moon's hit team. Chad and Alex were supposed to die, too, so they could not come back and claim what's rightfully theirs, what Nigel and Raymond stole from Paul, which was his business and the tunnel. Alex reluctantly believes Frank about this story, but Danielle continues to refuse to believe it. Alex, Chad, and Frank head out on Alex's boat. A few minutes after setting off, Alex's boat is approached by another boat. Alex allows three Chinese men aboard to look over a couple of cars that are on Alex's boat. As this is going on, two police boats approach. Alex throws the three Chinese men overboard, then while Alex heads to the boat's steering wheel, Chad and Frank send the cars overboard and blow the cars up. It seems that Alex is a smuggler. Later, Frank, Chad, Alex, and Danielle are at a restaurant, where Alex tells Chad and Frank that Danielle has been an employee of Nigel's company for the past 5 years. That's why Danielle refuses to believe Nigel's part in Paul and Katherine's murders. Chad takes a taxi cab out to the hotel where he and Frank have been staying, but before he can go inside, he is approached by a group of Chinese men who think he's Alex. Moon forces Chad into a car with Raymond, and taken to a boat yard. Raymond wants Alex's help in smuggling drugs, and he mistakenly has Moon place Chad in a cargo container and beat Chad up, trying to convince Alex to give in. Chad is then locked up in the container, taken downtown, and dumped out onto a street. After Chad is treated for his injuries, he and Alex decide that it's time to work together against Nigel and Raymond.