FORTUNE -- Everyone from Greece's squabbling political parties to Europe's central bankers are expressing faith that Greece will remain in the Euro. That's not surprising, since simply talking about how to manage an exit would spread panic, making the exit inevitable. But the panic is already here. Greece's departure from the Euro could happen within a couple of weeks, if not a few days.

The pressing problem isn't a splintered legislature that may balk at delivering the reforms that the IMF and European Community are demanding in exchange for the next tranche of bailout money. It's a disastrous, old-fashioned run-on-the bank. "For a year, Greeks have been sending their savings from Greek banks to foreign banks," says Robert Aliber, retired professor of international economics from the University of Chicago. "Now, the flood has reached a crescendo." Indeed on Monday alone, outflows from the Greek banks reached almost $900 million.

The flight of capital is sapping the deposits needed to refinance mortgages and small business loans, causing a full-blown credit crisis. Greeks are also extremely reluctant to spend their Euros on cars, dining or anything else, since they reckon those Euros will buy more at the supermarkets and auto lots in the weeks or months ahead. The disappearing consumer is further crippling the economy.

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Greece's exit is absolutely necessary. "Its prices and costs are far too high under the Euro, so it just cannot compete on international markets," says Aliber. "The Greeks have suffered far more through all these misguided bailouts than they've gained by lowering prices or costs." The political gridlock, argues Aliber, is actually a good thing because it will hasten abandoning a disastrously overvalued currency, just what's needed to get Greece growing again.

The mechanics of shelving the Euro for its own currency are pretty predictable. One day soon, imagine it's late on a Friday afternoon, the Greek government will declare all banks closed for the following week. By Monday, the legislature will vote an emergency law that designates a fixed exchange rate of, say, 1 drachma the Greek pre-Euro currency for each Euro. By Monday, all corporate and personal savings in Greek banks will be denominated in drachma.

The drachma will tumble in value, so that almost immediately, Greek consumers will need at least 1.5 Drachma to buy one Euro. A savings account that held 15,000 euros is now 15,000 Drachma. But those drachmas will soon fetch just 10,000 Euros. That's a "devaluation" of 33%. "That number is the low-end of the range for countries that exit a common currency," says Uri Dadush, an economist at the Carnegie Endowment.

What happens next is the pivotal issue, and top economists disagree strongly on Greece's post-Euro future. To be sure, this isn't a play by Aeschylus or Aristophanes where the audience knows the finale. Yanis Varoufakis of the University of Athens foresees a Greek tragedy in which a run on the banks is followed by a run on the drachma. "Greeks paid in drachma will go to the ATM then immediately exchange their drachma for Euros people have stashed in their freezers," says Varoufakis. He thinks that the drachma will keep plunging against foreign currencies, and Greeks will keep bailing, causing a new crisis of hyperinflation.

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But the disaster scenario isn't inevitable. "Other countries have left what's effectively a common currency zone without suffering hyperinflation," says Hans Humes, president of investment firm Greylock Capital, which holds Greek government bonds. Aliber thinks that Greece's exit will create the same growth dynamic that's recharged Iceland and Argentina, both of whom effectively shed overvalued currencies.

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Greece: The anatomy of a default