William D. Cohan on Wall Street and Main Street.

Now that we have pulled back sufficiently far from the near “destruction of the modern financial system” — as the former Treasury Secretary Henry Paulson described the events of 2008 in his new memoir, “On The Brink” — to focus on how to prevent such a calamity from recurring, the time has come to hear from those players in the drama who really know what happened and why.

Until people such as Warren Spector, the former co-president and head of the fixed-income division at Bear Stearns, and Dan Jester, a mysterious former Goldman Sachs banker turned Treasury official — among many others — come forward and share with us the roles they played before, during and after the crisis, there is little hope that the members of Congress working on financial reform legislation will be able to craft a bill that will succeed in its mission, and the longer they will spend dithering with the ill-conceived ideas being pushed by the former Fed Chairman Paul Volcker.

Who the heck is Dan Jester? And why isn’t he telling us what he did during the A.I.G. bailout and other pivotal moments of the banking crisis?

To date, these elusive but important Wall Street executives have kept an exceedingly low profile, hoping against hope that the whole thing just blows over. We can’t let that happen. There is just too much at stake now, and Wall Street has proved repeatedly over the past 40 years — since the firms went from private partnerships (where partners had their entire net worth on the line) to public companies (where bankers and traders were encouraged to take huge risks with other people’s money) — that it is incapable of regulating itself.

We need to get beyond the amusing political theater of the recent Financial Crisis Inquiry Commission hearings featuring tight-lipped Wall Street chief executives like Lloyd Blankfein of Goldman, John Mack of Morgan Stanley and Jamie Dimon of JPMorgan Chase — and the artfully crafted statements they compiled with the help of $1,000-an-hour Wall Street lawyers. We need to hear the nitty-gritty of what caused the crisis from the people who know why things happened the way they did but haven’t yet been asked to speak up by someone with subpoena power.

For instance, Warren Spector could provide chapter and verse on how Bear Stearns became a powerhouse in securitizing and trading home mortgages, and how the risks the firm took grew as that business became by far the company’s largest and most profitable. He could also shed light on the important role that Goldman Sachs played in the collapse of the two Bear Stearns hedge funds in July 2007 after Goldman’s traders provided Bear’s executives, in April 2007, with new, lower valuations that Goldman had put on the mortgage securities in the hedge funds. One assumes that Spector could tell us what kind of panic ensued inside Bear as a result. These lower marks led the managers to reduce the funds’ Net Asset Value in April 2007, which caused investors to head to the exits.

Spector could also share his ideas on how to re-open the securitization market without repeating past mistakes. This is the kind of valuable information that Jimmy Cayne, the longtime top dog at Bear Stearns (it was he who fired Spector in August 2007), or Alan Schwartz, who was Bear’s chief executive in the final months of the firm’s existence in 2008, simply cannot provide. Why hasn’t Spector been asked to share his knowledge?

As for Jester, he knows plenty, and isn’t talking. As Representative Marcy Kaptur, an Ohio Democrat, pointed out at the Congressional hearing about American International Group on January 27, between Sept. 14, 2008 and Nov. 26, 2008 — the darkest days of the financial crisis — Tim Geithner, then head of the Federal Reserve Bank of New York and now Treasury Secretary, spoke on the phone with Jester 103 times. Paulson — not Ben Bernanke, the Chairman of the Federal Reserve, or Christopher Cox, the Chairman of the Security and Exchange Commission — was the only person to whom Geithner spoke more often.

Who the heck is Dan Jester? In “On the Brink,” Paulson first identifies him only as a “contractor” to the Treasury Department while Paulson was secretary. Paulson then elaborates that Jester had previously worked for him at Goldman, where he had been a financial-institutions banker and a “key member” of the firm’s risk committee. According to Paulson, the “unflappable and brilliant” Jester retired from Goldman in spring 2005 and moved to Austin, Tex.

Paulson writes that after he became Treasury secretary, he tried to recruit Jester to Washington as an assistant secretary but Jester declined. When Robert Steel, a former Goldman partner and a Paulson confidante, left Treasury to become chief executive of Wachovia in the summer of 2008, Paulson “impressed” on Jester “the nature of our emergency.” Jester changed his mind and came to Washington “even though it meant leaving his family behind for six months.”

During his time at Treasury, Jester seems to have had his finger in every pie: the rescue of Fannie Mae and Freddie Mac, the bankruptcy of Lehman Brothers, the A.I.G. calamity, the decisions to bailout Citigroup, G.M. and Chrysler, and the creation of the Troubled Asset Relief Program. For Fannie and Freddie, Paulson credits Jester with the “inspired idea” of creating a “keepwell” agreement that allowed the Treasury to continually provide financing to those companies “no matter how much they lost long into the future.” During that fateful weekend of Sept. 13 and 14 of 2008, Jester tried to negotiate deals for Lehman with both Bank of America and Barclays — to no avail — before the 158-year old securities firm collapsed into bankruptcy.

Jester quickly turned his attention to A.I.G.. He got a call on that Sunday afternoon, from the billionaire private-equity maven J. Christopher Flowers, who had been the head of the financial-institutions group at Goldman when Jester worked there, who said he’d made a bid to acquire A.I.G. to keep it from failing. Paulson’s book makes no mention beyond that of the role Jester played in the bailout of the insurer — including his being moved from the Treasury to A.I.G.’s offices for a period of time. One former A.I.G. executive told me that Jester was calling many of the shots at the insurer between mid-September, when the New York Fed decided to go ahead with the bailout, and the end of October 2008 ,when Jester was replaced at A.I.G. by another Treasury official because, according to The New York Times, of Jester’s “stockholdings in Goldman Sachs.” Goldman ended up with $14 billion in counterparty payments from A.I.G. “He was Paulson’s man,” the former A.I.G. executive told me. “He was the Treasury’s representative, and he was at every meeting” during that mid-September weekend.

At one point, on the following Monday, Sept. 15, as the A.I.G. situation was spiraling out of control, Jester phoned the three major credit-rating agencies and asked them to hold off from downgrading A.I.G. any further, since that additional downgrade would force the insurer to make even more collateral payments on the spot to counterparties, further depleting its dwindling cash. Jester’s efforts weren’t persuasive. “It was pathetic,” the former A.I.G. executive told me. Then, after the Citigroup executive (and former Treasury secretary and Goldman co-senior partner) Robert Rubin called Paulson to say “Citi was not being given clear direction,” Jester was off to help Paulson and Rubin craft the creative solution to “ring-fence” $306 billion of Citigroup’s most-toxic assets before Thanksgiving 2008. This was, of course, just weeks after Jester had helped Paulson design and unroll TARP.

These days, Jester is back in Austin, where he is being careful not to return calls from those seeking answers to legitimate questions about what role he played in what happened. Perhaps he would return a call from Geithner asking him to appear on Capitol Hill to answer some questions. After all, he’s answered that call 103 times before.