Mr Lau was a corrupt banker who was in league with several of Gotham's criminals. Although based in Hong Kong, he visited Gotham to pitch an investment opportunity to Wayne Enterprises. While there, he decided to help out the criminal underworld - knowing that Harvey Dent was going after their money, he had it all transferred to a large account in his name.
He then made a proposal to several of the criminal underworld's leaders, such as Sal Maroni, the Chechen and Gambol - keep all of the money with him, and while he was in Hong Kong he was far from Dent's jurisdiction. However the Joker turned up during the proposal, and warned that Batman would find Lau and make him talk.
Lau arrived back at Hong Kong, where he was visited by Lucius Fox to discuss the investment. Fox turned him down, and Lau was irritated that he travelled all the way just to refuse him. He did not know, however, that Fox was using the visit to scope out the inside of his building, and that night Batman broke in and kidnapped Lau using sky hook technology. He was delivered to Harvey Dent the next morning.
Dent and Rachel Dawes then questioned Lau, who gave up all the mobsters he was in league with. He was kept in the Major Crimes Unit when all the arrests were being made. Some time later, the Joker was in the building when he set off a bomb and broke Lau out. He then tied him up atop a giant mound of money, and set the stack ablaze. Lau died along with all of his money.