My story about a basically sound bank beset by a crisis of confidence, which can be rescued with a temporary loan from the Fed, is more or less what happened to the financial system as a whole in 1998. Russia’s default led to the collapse of the giant hedge fund Long Term Capital Management, and for a few weeks there was panic in the markets.

Image Paul Krugman Credit... Fred R. Conrad/The New York Times

But when all was said and done, not that much money had been lost; a temporary expansion of credit by the Fed gave everyone time to regain their nerve, and the crisis soon passed.

In August, the Fed tried again to do what it did in 1998, and at first it seemed to work. But then the crisis of confidence came back, worse than ever. And the reason is that this time the financial system  both banks and, probably even more important, nonbank financial institutions  made a lot of loans that are likely to go very, very bad.

It’s easy to get lost in the details of subprime mortgages, resets, collateralized debt obligations, and so on. But there are two important facts that may give you a sense of just how big the problem is.

First, we had an enormous housing bubble in the middle of this decade. To restore a historically normal ratio of housing prices to rents or incomes, average home prices would have to fall about 30 percent from their current levels.

Second, there was a tremendous amount of borrowing into the bubble, as new home buyers purchased houses with little or no money down, and as people who already owned houses refinanced their mortgages as a way of converting rising home prices into cash.

As home prices come back down to earth, many of these borrowers will find themselves with negative equity  owing more than their houses are worth. Negative equity, in turn, often leads to foreclosures and big losses for lenders.