At some point, I gave up waiting for the end. There was no scandal or reversal, I assumed, that could sink the system.

Then came Meredith Whitney with news. Whitney was an obscure analyst of financial firms for Oppenheimer Securities who, on October 31, 2007, ceased to be obscure. On that day, she predicted that Citigroup had so mismanaged its affairs that it would need to slash its dividend or go bust. It’s never entirely clear on any given day what causes what in the stock market, but it was pretty obvious that on October 31, Meredith Whitney caused the market in financial stocks to crash. By the end of the trading day, a woman whom basically no one had ever heard of had shaved $369 billion off the value of financial firms in the market. Four days later, Citigroup’s C.E.O., Chuck Prince, resigned. In January, Citigroup slashed its dividend.

From that moment, Whitney became E.F. Hutton: When she spoke, people listened. Her message was clear. If you want to know what these Wall Street firms are really worth, take a hard look at the crappy assets they bought with huge sums of ­borrowed money, and imagine what they’d fetch in a fire sale. The vast assemblages of highly paid people inside the firms were essentially worth nothing. For better than a year now, Whitney has responded to the claims by bankers and brokers that they had put their problems behind them with this write-down or that capital raise with a claim of her own: You’re wrong. You’re still not facing up to how badly you have mismanaged your business.

Rivals accused Whitney of being overrated; bloggers accused her of being lucky. What she was, mainly, was right. But it’s true that she was, in part, guessing. There was no way she could have known what was going to happen to these Wall Street firms. The C.E.O.’s themselves didn’t know.

Now, obviously, Meredith Whitney didn’t sink Wall Street. She just expressed most clearly and loudly a view that was, in retrospect, far more seditious to the financial order than, say, Eliot Spitzer’s campaign against Wall Street corruption. If mere scandal could have destroyed the big Wall Street investment banks, they’d have vanished long ago. This woman wasn’t saying that Wall Street bankers were corrupt. She was saying they were stupid. These people whose job it was to allocate capital apparently didn’t even know how to manage their own.

At some point, I could no longer contain myself: I called Whitney. This was back in March, when Wall Street’s fate still hung in the balance. I thought, If she’s right, then this really could be the end of Wall Street as we’ve known it. I was curious to see if she made sense but also to know where this young woman who was crashing the stock market with her every utterance had come from.

It turned out that she made a great deal of sense and that she’d arrived on Wall Street in 1993, from the Brown University history department. “I got to New York, and I didn’t even know research existed,” she says. She’d wound up at Oppenheimer and had the most incredible piece of luck: to be trained by a man who helped her establish not merely a career but a worldview. His name, she says, was Steve Eisman.

Eisman had moved on, but they kept in touch. “After I made the Citi call,” she says, “one of the best things that happened was when Steve called and told me how proud he was of me.”

Having never heard of Eisman, I didn’t think anything of this. But a few months later, I called Whitney again and asked her, as I was asking others, whom she knew who had anticipated the cataclysm and set themselves up to make a fortune from it. There’s a long list of people who now say they saw it coming all along but a far shorter one of people who actually did. Of those, even fewer had the nerve to bet on their vision. It’s not easy to stand apart from mass hysteria—to believe that most of what’s in the financial news is wrong or distorted, to believe that most important financial people are either lying or deluded—without actually being insane. A handful of people had been inside the black box, understood how it worked, and bet on it blowing up. Whitney rattled off a list with a half-dozen names on it. At the top was Steve Eisman.

Steve Eisman entered finance about the time I exited it. He’d grown up in New York City and gone to a Jewish day school, the University of Pennsylvania, and Harvard Law School. In 1991, he was a 30-year-old corporate lawyer. “I hated it,” he says. “I hated being a lawyer. My parents worked as brokers at Oppenheimer. They managed to finagle me a job. It’s not pretty, but that’s what happened.”

He was hired as a junior equity analyst, a helpmate who didn’t actually offer his opinions. That changed in December 1991, less than a year into his new job, when a subprime mortgage lender called Ames Financial went public and no one at Oppenheimer particularly cared to express an opinion about it. One of Oppenheimer’s investment bankers stomped around the research department looking for anyone who knew anything about the mortgage business. Recalls Eisman: “I’m a junior analyst and just trying to figure out which end is up, but I told him that as a lawyer I’d worked on a deal for the Money Store.” He was promptly appointed the lead analyst for Ames Financial. “What I didn’t tell him was that my job had been to proofread the ­documents and that I hadn’t understood a word of the fucking things.”

Ames Financial belonged to a category of firms known as nonbank financial institutions. The category didn’t include J.P. Morgan, but it did encompass many little-known companies that one way or another were involved in the early-1990s boom in subprime mortgage lending—the lower class of American finance.

The second company for which Eisman was given sole responsibility was Lomas Financial, which had just emerged from bankruptcy. “I put a sell rating on the thing because it was a piece of shit,” Eisman says. “I didn’t know that you weren’t supposed to put a sell rating on companies. I thought there were three boxes—buy, hold, sell—and you could pick the one you thought you should.” He was pressured generally to be a bit more upbeat, but upbeat wasn’t Steve Eisman’s style. Upbeat and Eisman didn’t occupy the same planet. A hedge fund manager who counts Eisman as a friend set out to explain him to me but quit a minute into it. After describing how Eisman exposed various important people as either liars or idiots, the hedge fund manager started to laugh. “He’s sort of a prick in a way, but he’s smart and honest and fearless.”