In January, a unit of Alcoa Inc., the biggest U.S. aluminum producer, pleaded guilty to foreign bribery charges brought by the U.S. Justice Department. Alcoa also settled claims by the Securities and Exchange Commission and agreed to pay a $384 million fine -- the fifth-largest such penalty ever. The Alcoa subsidiary admitted to paying bribes to government officials in Bahrain for more than a decade to win contracts to sell alumina, a compound essential in making aluminum, to the Persian Gulf state's processing plant. Not named and not charged in the case was the person who made those payments, whom the Justice Department identified in court only as Consultant A." In the thriving business of global bribery -- which the World Bank says amounts to $1 trillion in illicit payments annually -- guilty pleas like the one by Alcoa's unit are rare. Rarer still are convictions against the people who actually arrange and deliver the payments. Most of the time, these brokers aren't even named. The Alcoa guilty plea -- together with related cases in the U.K. and Norway -- provides an unusual window into the modus operandi of the middlemen who shuttle between companies and governments striking deals. Before the U.S. announced the fine against Alcoa, U.K. prosecutors in October 2011 charged Victor Dahdaleh, a London-based businessman, with laundering money and making improper payments to officials in Bahrain related to Alcoa contracts. Dahdaleh was acquitted in December after the prosecution dropped its case. While the U.S. plea agreement doesn't identify Dahdaleh as Consultant A, it does show that a company owned by Dahdaleh played a role in the Alcoa unit payments to Alba.