It sounds like a plotline straight out of Oliver Stone's Wall Street: On March 1, the SEC charged Rajat Gupta, a former Goldman Sachs director described as the "ultimate corporate insider," with illegally handing confidential investor information over to a hedge fund. Here, a guide to how the alleged dealing went down, who stands to win and lose, and how Warren Buffett got involved:

First things first. What is insider trading?
The term refers to any instance when a financial trader takes advantage of confidential insider knowledge to make money from the impact of that information on the market.

And what is Gupta accused of?
Gupta is accused of providing hedge fund manager Raj Rajaratnam with privileged information gleaned from Goldman Sachs board meetings — information that allowed Rajaratnam to make huge trades in Goldman stock before it was announced to the market. For instance, Gupta clued Rajaratnam into the news that Warren Buffett's Berkshire Hathaway was making a $5 billion investment in the bank just moments after Goldman's board received word. The illicit dealing, says Felix Salmon at Seeking Alpha, "seems to have been pretty blatant."

How much money did Gupta make?
The SEC alleges that the insider trading generated more than $18 million in profits and loss avoidance — though it's unclear exactly how much, if any, went into Gupta's pockets. But the Goldman Sachs director was an investor in Rajaratnam's hedge fund, and had "other potentially lucrative business interests" with him, says the SEC.

And this guy's a real Wall Street big shot, right?
He's "one of the most connected people in corporate America that you've never heard of," says John Carney at CNBC. He spent 34 years at consultant powerhouse McKinsey, rising to become head of the firm. In 2001, he left to sit on the board of five well-known companies, including Goldman Sachs, Procter & Gamble, and American Airlines parent AMR. He is chairman of the International Chamber of Commerce, and sits on the boards of Wharton, Harvard and MIT's business schools. "Never before in the history of US securities laws has anyone this established, this well-connected, this close to the central core of American capitalism faced such charges."

Has corporate America turned its back on him now?
Not yet. Gupta resigned from Goldman Sachs' board last year when the investigation began, and stood down voluntarily from P&G's board when these charges were announced. But he remains on the board of two public companies, and serves as non-executive chairman of a third.

Why'd he do it?
It's a mystery, says Carney at CNBC. Gupta was already a top dog on Wall Street. "He doesn't need money, access, prestige or any favors at all." Maybe it was just hubris, says Evan Newmark at The Wall Street Journal. "It's hard not to think it was Gupta's own success that is in fact now bringing him down." Having risen to the pinnacle of the American corporate world, he was arrogant enough to think the rules didn't apply to him.

What does Gupta say about all this?
He calls the allegations "totally baseless," and says he is confident he will be found not guilty. He also claims to have lost $10 million from Rajaratnam's hedge fund at the time the events took place. He will face trial on March 8.

Sources: SEC, CNBC, Seeking Alpha, Forbes, Economist, Business Insider, Fortune, Wall Street Journal