The Mob Summit was hosted by Lau to establish that he was going to watch the cash of Gotham City's underworld.
History[]
To deal with the increasing pressure put on their gangs by Harvey Dent, Lieutenant Gordon and Batman, the three dominant factions of the Mobs in Gotham agreed put aside their differences to a daytime summit. Sal Maroni (Falcone's successor to the Italian Mob) the Chechen (Chechyan Mob) and Gambol (African-American Mob) met in an abandoned soup kitchen where Lau, a Chinese Mafia accountant, was hosting the conference via TV from his private jet en route to Hong Kong. Lau mentioned a recent robbery of one of their deposits by the Joker ("A relatively small amount- 68 million") but Maroni quickly dismissed him as a 'two-bit whack job' and a 'nobody', while the real threat was that the police were tracing their funds.
Lau explained that Gordon's use of corrupt cops to buy drugs- using lightly irradiated bills provided by Batman- allowed the police to identify their banks. From those same corrupt cops and sources in the D.A.'s office, however, Maroni had successfully been alerted that the cops were preparing to seize all the Mob's funds that very day- and Harvey Dent's prosecution had taken out most of the Mob's other accountants. The plan was that Lau would move all their funds to one secure location, and that he would return to Hong Kong; thus, both he and the money would be beyond the reach of Dent's prosecution, while the Chinese would be unlikely to extradite him. Both Gambol and the Chechen (who had not been in on this plan) were visibly distrustful, especially when they learned that Lau had already moved all the money without their permission. Meanwhile, in the banks, Gordon's forces seized the vaults only to find the marked bills they had used and nothing else.
At this point, the Joker entered the room (somehow having bypassed the security check) and began mocking the plan. Gambol's ire rose at the Joker's offer of a magic trick, but when his thug moved to attack the Joker killed him in a heartbeat (by slamming his head against a table and embedding a pencil in his eye socket and brain- thus, the magic trick of 'making a pencil disappear'). When his remarks continued to anger Gambol, the Chechen told him to sit down, showing interest in hearing the Joker's proposition.
The Joker eagerly obliged, pointing out that one year ago the cops would never have dared to pull off a scheme, nore would the mob bosses now need to hold peace summits specifically in the daytime; it was ultimately Batman who had changed the picture. Also, since Batman- despite having a rule never to kill- could go beyond jurisdiction, the Mob's money was not safe even in Hong Kong with Lau, whom the Joker derided as a 'squealer'. Unnerved by the Joker's accusations and erratic behavior, Lau ended his connection to the conference. When the Chechen asked what the plan was, the Joker replied, "It's simple. We- uh- kill the Batman."
At this, most of the mob under-bosses began to laugh; nobody had the first clue how to find Batman, let alone battle him to the death. Sal Maroni sarcastically asked why the Joker hadn't already done so if it was simple; the Joker promptly answered, "If you're good at something, never do it for free." Intrigued by his confidence, the Chechen asked for his price, which turned out to be half the Mob's funds. The Joker's reminder of their precarious financial position- coupled with a barbed insult- finally pushed Gambol over the edge, but as his men rose to attack the Joker revealed his insurance policy- an array of grenades and explosives strapped to his chest. Gambol declared that he would put a bounty on the Joker's head- $500,000 for his death, or $1,000,000 alive "so I can teach him some manners first!" Calmly, the Joker suggested the Mob give him a message when they were more receptive to his offer and left them his calling card (a Joker card), leaving via the back entrance.