IN 1976, Mario J. Gabelli, then a red-headed 34-year-old research analyst, took one of his regular trips to Branford, Conn., to meet with Frederick J. Mancheski, then chairman and chief executive of Echlin Inc., an auto parts company he covered. But on that visit, Mr. Gabelli had something to sell: himself.

"He came in one day and said he was thinking of starting his own firm to manage money," Mr. Mancheski, now 79, recalled in a recent interview. "I told him I thought he had the know-how and he asked me if I'd be interested in investing in it. I was the first backer." He sent him a $50,000 check.

Mr. Gabelli, now 63 with a shock of white hair, has gone on to become one of the nation's most successful and powerful mutual fund managers; his company, Gamco Investors, formerly Gabelli Asset Management, has huge stakes in some of the world's largest media companies, including Time Warner and Viacom. Barron's once listed him among the "world's greatest stock pickers." By following a value-investment philosophy not that different from Warren Buffett's, he has come to be known on Wall Street as "Super Mario."

Mr. Gabelli made his name and fortune by being a vocal champion of shareholder rights, often railing in the press against companies to push them to follow his agenda. He has said he "got the idea from the Pilgrims of the 17th century, who would put you in the stocks when you committed a crime to serve your appropriate tour of duty and expose you to public ridicule."

But today his own $28 billion empire, based in Rye, N.Y., is under attack, accused of an assortment of corporate abuses. And his accuser is perhaps his unlikeliest foe: Mr. Mancheski.

Although he is the second-largest investor in Mr. Gabelli's private holding company, Mr. Mancheski has filed suit against it, contending that Mr. Gabelli and his firm's directors "are guilty of looting the assets of the company, breaching their fiduciary duties to its shareholders and oppressing its minority shareholders."

The suit offers a rare glimpse inside Mr. Gabelli's mutual fund kingdom, uncovering reams of previously confidential documents and highlighting other records that suggest his business may be run like so many of the companies that he has long criticized as disenfranchising shareholders.

They show, among other things, that Mr. Gabelli has spun a complicated web of private and public businesses that he has used to pay himself and his sons hundreds of millions of dollars in salary and management fees. In some cases, the compensation goes far beyond what has ever been made public in the company's filings.

It is certainly no secret that Mr. Gabelli, a graduate of Fordham University and Columbia Business School, is well paid. His publicly disclosed income for 2004 was $55 million - "enormous by any standard," said Rachel Barnard, an analyst at Morningstar - and in 2002, he took home $87 million in cash when the firm's net income was only $53.3 million.

Nor is it a secret that outsiders have previously raised questions about his governance. Morningstar, while acknowledging that his company's stock has outperformed the Standard & Poor's 500-stock index by a wide margin since 1999, has nonetheless consistently given his funds a near-flunking "D" grade for stewardship. The low mark was based in part on Mr. Gabelli's lavish compensation and tight control over the business.

But Mr. Mancheski's lawsuit, which was filed with David M. Perlmutter, another of the firm's original investors and a former lawyer for the company, takes the allegations much further. Of course, the goal of the lawsuit is to force Mr. Gabelli to pay the men tens of millions of dollars that they say they are owed. And the men, both of whom are already wealthy, may have been motivated to make some of the lawsuit's most strident accusations in hopes of being able to extract a generous settlement from Mr. Gabelli. Mr. Mancheski and Mr. Perlmutter own nearly 10 percent of Mr. Gabelli's private company.

Mr. Gabelli declined to be interviewed for this article. A spokesman for him called the suit "tantamount to greenmail" and suggested that the men were trying to "reap huge additional gains at the expense of the other shareholders." Nonetheless, the judge overseeing the case, in State Supreme Court in Westchester County, has denied Mr. Gabelli's requests to have it dismissed. The case is expected to be tried later this year, unless a settlement is reached first.

TRYING to understand Mr. Gabelli's empire is like trying to solve a complex jigsaw puzzle whose pieces have been scattered. There is the widely known publicly traded Gamco Investors, which houses the famous family of mutual funds that is the crown jewel of his business. Then there is a private company, called Gabelli Group Capital Partners, or G.G.C.P., that owns majority control of Gamco and operates several other ancillary investment businesses.

Mr. Gabelli is the majority owner of G.G.C.P. and therefore also has majority control of Gamco. While Gamco reports its earnings, compensation for executives and other information to the public, G.G.C.P. does not. As a private company, it doesn't have to.

As a result, investors in Gamco would never know, for instance, that Mr. Gabelli takes the equivalent of two salaries: one from Gamco and another from G.G.C.P., a curious idea since G.G.C.P.'s main business is, well, Gamco. Documents from the case show that beyond Mr. Gabelli's public salary at Gamco, he pays himself 20 percent of G.G.C.P.'s pretax revenue as a "management fee," which he shares with his sons Marc and Matthew, both of whom serve on G.G.C.P.'s board. The G.G.C.P. management fee alone has produced more than $20 million for Mr. Gabelli and his sons since 1999.

In addition, Mr. Gabelli is the chairman and chief executive of another public company, called Lynch Interactive, a multimedia company that shares office spare with Gamco. Mr. Gabelli's son Marc is the chairman of the Lynch Corporation, the one-time parent of Lynch Interactive, a public company that shares office space with G.G.C.P. Filings show that Lynch Interactive and the Lynch Corporation have paid Mario Gabelli over $7 million since 1999.

All of this raises a question: How can one person be in so many places at one time? To be sure, senior executives often have roles outside of their company on boards of other businesses or charities, but it is rare to see the same executive with the title of chief executive for three separate businesses, two of them publicly traded entities. According to Mr. Gabelli's employment contract with Gamco, he is required to spend "the substantial majority of his working time" operating that business.

Mr. Gabelli's generous compensation poses a particular problem for Mr. Mancheski and Mr. Perlmutter. Both contend that as minority shareholders in G.G.C.P., they can only watch helplessly as Mr. Gabelli has paid himself handsomely with what they say is at least partly their money. While Mr. Mancheski accepts that he had agreed to Mr. Gabelli's initial pay formula, he questions its suitability for the leader of a company that has grown so large.

"If I had been advised in 1977 that Mr. Gabelli would pay himself 40 percent of gross revenues generated by him and 20 percent of the company's pretax revenue regardless of how successful the company became, how many additional executives and employees were hired, or how much money that formula produced in any one year, I would not have invested," Mr. Mancheski said in an affidavit. "Although such a compensation formula might have been appropriate for the chief executive of a start-up company with virtually no business, it is a wholly inappropriate formula for the chief executive of a mature and successful company."

So why doesn't Mr. Mancheski just sell his stake in the business?

That is the heart of his problem and, in turn, the basis of his case. He can't.

The tension goes back to when Mr. Mancheski and Mr. Perlmutter first invested with Mr. Gabelli. At the time, there were very few conditions attached to the investments. Mr. Mancheski and Mr. Perlmutter say they believed that at some point they would be able to sell their shares for whatever they were worth or transfer them to members of their family. For more than two decades, neither man had any reason to sell his shares - and Mr. Gabelli has been on a long hot streak.

In 1999, Mr. Gabelli took his company public. It was supposed to be a huge payday for everyone. Mr. Mancheski's original investment in 1976 would have turned into nearly $100 million, if not more. But at the last minute, Mr. Gabelli restructured the offering so that only the company's mutual fund business would be taken public - leaving the company's ancillary investment businesses remaining in the private company, and preventing its minority investors from being able to cash out.

A review of the company's filings with the Securities and Exchange Commission shows that Mr. Gabelli originally filed to take the entire private company public, which would have given all G.G.C.P. shareholders publicly traded stock. But then he changed the arrangement, transferring its operating businesses into a new subsidiary that then issued 20 percent of its stock to the public and 80 percent to G.G.C.P. The reorganization not only kept the company's minority shareholders like Mr. Mancheski from reaping the benefits of the I.P.O.; it also made it possible for G.G.C.P. to avoid having to make public disclosures.

It is not clear whether the purpose of changing the structure of the offering was to disenfranchise Mr. Gabelli's original minority shareholders. Executives involved in the offering suggest that the offering was restructured, in part, for tax purposes and to make the company more attractive to new investors. Still, the byproduct of the restructured offering was to preclude G.G.C.P.'s shareholders from being able to sell their shares.

While Mr. Mancheski and Mr. Perlmutter received nothing directly from the offering - except for the theoretical increase in the value of the company - Mr. Gabelli paid himself a $50 million bonus in cash. At the time of the offering, Goldman Sachs, which was underwriting it, refused to work on the project unless Mr. Gabelli lowered the formula for his compensation. The formula had called for Mr. Gabelli to be paid 20 percent of pretax profits. To placate Goldman, he dropped his demand to only 10 percent of pretax profits and took the $50 million one-time payment.

IN 2003, Mr. Gabelli went to Mr. Mancheski's house for breakfast. Mr. Mancheski said he told Mr. Gabelli that he wanted to sell his shares and transfer others to his children and grandchildren as part of his estate planning. According to Mr. Mancheski, Mr. Gabelli had a surprise for him: he told him that he couldn't. Mr. Gabelli said Mr. Mancheski's shares were restricted and could not be sold or transferred without the approval of the board - and being that he controlled the board, he was not approving their sale to anyone but the company.

Mr. Mancheski was given two choices: he could sell his shares back to Mr. Gabelli, using a predetermined "book value" formula that Mr. Mancheski says would leave him with only about a third of the more than $100 million that he says his stake is worth, based on the share price of Gamco. Or he could hold on to them until he dies, at which time they are required to be sold back to Mr. Gabelli at the same price anyway. Neither choice is that appealing.

"Mario's a stubborn guy," Mr. Mancheski said.