On August 3, 2005, tech entrepreneur Vernon Jackson walked outside, into a warm and hazy Kentucky morning. No one watching his modest red brick home from afar—as someone certainly was that day—would have noticed anything untoward. A sign staked in Jackson’s lawn displayed the Ten Commandments in big letters. Jackson opened the door of his car, a 1997 Mercedes-Benz S600, one of the few things he’d held on to from his paper-millionaire days. As an inventor, Jackson always had to prove the value of his ideas. And as a black man who’d lived his whole life in the South, he knew the power of outward appearances.

Physically, Jackson cut an imposing figure: over six feet tall, bald, thick-necked, and broad-shouldered. (“He is a David that looks like a Goliath,” says a friend.) He’d turned 53 the month before and was trying to get his considerable weight under control. Jackson and his wife of more than three decades, Denise, liked to take a brisk daily walk. On this morning, as they often did, the couple drove to a park not far from their home in Louisville, and it was there that F.B.I. agents intercepted them, flashing their badges and carrying a search warrant.

Vernon Jackson didn’t yet realize it, but he was a central figure in one of the most sprawling corruption investigations in recent American history, a tale of bribery and international financial chicanery that stretched from Louisville to Washington to Africa. At that very moment, the F.B.I. was conducting simultaneous raids in three states and the District of Columbia. Out in Maryland horse country, one team of investigators was mounting a search of a $2 million mansion belonging to Atiku Abubakar, then the vice president of Nigeria. Another was descending on the New Orleans residence of William Jefferson, a Democratic congressman from Louisiana.

Jefferson was a leader of the Congressional Black Caucus and a member of the powerful House Ways and Means Committee. For years, he had acted as a tireless promoter of Jackson’s company, iGate, which had developed electronic components designed to transform ordinary copper telephone wires into conduits for extraordinary amounts of data. Jefferson’s advocacy had pushed Jackson—who’d already ridden an initial public offering to fortune once before, only to see the company crash into bankruptcy—to the brink of the biggest coup of his career: a $200 million-a-year deal to provide high-speed internet services to consumers in Nigeria. But according to the government, Jefferson’s interest in iGate was far from altruistic. Recently unsealed affidavits filed in support of the F.B.I.’s search warrants suggest that the congressman was a secret shareholder in iGate. More than that, the affidavits say Jefferson had conspired to further the deals by bribing Vice President Abubakar.

That morning, Jefferson, just awoken, answered his door unshaven and barefoot. As F.B.I. agents stuffed evidence into boxes, the congressman, a dour man at the best of times, sat sullenly at his kitchen table, flipping through papers. Then he moved to a living room recliner, where he nonchalantly stuffed the documents into a blue bag. Confronted by an F.B.I. agent, he turned over the papers, which included an iGate fax sent just that morning that sought Jefferson’s input on an equipment purchase—proof, prosecutors later alleged, of the congressman’s ownership interest.

The most incriminating find, however, came at Jefferson’s Washington townhouse. In drawers, in trash cans, and in stacks on the floor, F.B.I. agents found numerous documents relating to iGate’s African deals. Then the agents opened the freezer. Inside a Boca Burger box, they found two stacks of cash wrapped in aluminum foil. More money was stuffed into a Pillsbury piecrust box. There was $90,000 in all.

In the end, that’s all people remembered: the cash in the freezer. As details leaked into the pages of the Washington Post and the New Orleans Times-Picayune, the story of the congressman with 90 grand in his icebox quickly became a national joke, another colorful example of Capitol Hill corruption. Yet the case would prove to have implications far more momentous than a punch line. In Washington, it would lead to William Jefferson’s indictment and a constitutional clash over the executive branch’s powers to investigate members of Congress. In Nigeria, it would scuttle Atiku Abubakar’s campaign to become the next elected leader of one of the world’s largest oil producers. And back in Louisville, it would upend the life of a flawed man with a promising idea.