We may never know for sure whether the Federal Reserve's rescue of Bear Stearns averted a seizure of the $516 trillion derivatives system, the ultimate Chernobyl for global finance.
"If the Fed had not stepped in, we would have had pandemonium," said James Melcher, president of the New York hedge fund Balestra Capital.
"There was the risk of a total meltdown at the beginning of last week. I don't think most people have any idea how bad this chain could have been, and I am still not sure the Fed can maintain the solvency of the US banking system."
All through early March the frontline players had watched in horror as Bear Stearns came under assault and then shrivelled into nothing as its $17bn reserve cushion vanished.
Melcher was already prepared - true to form for a man who made a fabulous return last year betting on the collapse of US mortgage securities. He is now turning his sights on Eastern Europe, the next shoe to drop.
"We've been worried for a long time there would be nobody to pay on the other side of our contracts, so we took profits early and got out of everything. The Greenspan policies that led to this have been the most irresponsible episode the world has ever seen," he said.
Fed chairman Ben Bernanke has moved with breathtaking speed to contain the crisis. Last Sunday night, he resorted to the "nuclear option", invoking a Depression-era clause - Article 13 (3) of the Federal Reserve Act - to be used in "unusual and exigent circumstances".
The emergency vote by five governors allows the Fed to shoulder $30bn of direct credit risk from the Bear Stearns carcass. By taking this course, the Fed has crossed the Rubicon of central banking.
To understand why it has torn up the rule book, take a look at the latest Security and Exchange Commission filing by Bear Stearns. It contains a short table listing the broker's holding of derivatives contracts as of November 30 2007.
Bear Stearns had total positions of $13.4 trillion. This is greater than the US national income, or equal to a quarter of world GDP - at least in "notional" terms. The contracts were described as "swaps", "swaptions", "caps", "collars" and "floors". This heady edifice of new-fangled instruments was built on an asset base of $80bn at best.
On the other side of these contracts are banks, brokers, and hedge funds, linked in destiny by a nexus of interlocking claims. This is counterparty spaghetti. To make matters worse, Lehman Brothers, UBS, and Citigroup were all wobbling on the back foot as the hurricane hit.
"Twenty years ago the Fed would have let Bear Stearns go bust," said Willem Sels, a credit specialist at Dresdner Kleinwort. "Now it is too interlinked to fail."
The International Swaps and Derivatives Association says the vast headline figures in the contracts are meaningless. Positions are off-setting. The actual risk is magnitudes lower.
The Bank for International Settlements uses a concept of "gross market value" to weight the real exposure. This is roughly 2 per cent of the notional level. For Bear Stearns this would be $270bn, or so.
"There is no real way to gauge the market risk," said an official