NEW YORK (FORTUNE) - For the first four weeks of the Enron trial, it was a constant refrain from the lawyers for Ken Lay and Jeff Skilling: What did the prosecution witnesses really know about what had gone on in the bowels of Enron's business?

The defense tried to cast two former Enron investor-relations executives as too far removed from operations to know much -- and Ken Rice, the former broadband chief, as simply having checked out. But on Monday, prosecutors presented a pair of witnesses who saw how the sausage was being made -- and what they described was simply unfit for consumption.

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First up was Wes Colwell, former chief accounting officer for Enron North America, Enron's highly profitable trading business. Court started, as usual, promptly at 8:30 a.m., and by 8:45 a.m., Colwell was testifying about how he had manipulated earnings. In particular, he was describing how he'd tapped a "prudency" reserve account to boost Enron's reported earnings for the second quarter of 2000 by two cents a share -- enough to beat Wall Street expectations.

Colwell recounted how word had come down from corporate on two separate occasions in a span of days during July 2000 that the trading business needed to produce an extra penny of profit -- an extra $7 million on each occasion. On July 17, he e-mailed David Delainey, the CEO of Enron North America (also likely to take the stand by week's end), to report news of the second request, even though the quarter's books were already closed.

"Speaking of closed," Colwell noted, "it looks like we may be looking to beat the street by two cents instead of a penny. I understand [Enron chief accounting officer Rick] Causey spoke to Skilling today and this was his preference."

Under questioning from Enron Task Force chief Sean Berkowitz, Colwell traced how the reserve reductions were recorded in company accounting ledgers, reducing a $70 million reserve set up to settle a disputed contract down to $56 million. Earnings had been increased, he noted, even though nothing about the economic reality of Enron's business had changed.

Then it happened again. In a January 2, 2001 e-mail to Delainey -- after the end of the fourth quarter -- Colwell noted plans to "make any necessary adjustments" to reserves "to make our targets as promised to Corp. FYI, we will likely get some pressure to overproduce more for the purpose of beating the analysts' estimates." He testified that the size of a key reserve amount for his division was determined by whatever was left over after the company had booked what it needed to please Wall Street.

It was illegal to use reserves this way to "land the quarter," Colwell testified; reserve levels are supposed to be set independent of a company's earnings targets. Colwell, who has admitted manipulating Enron's earnings, has been fined $500,000 by the SEC, lost his CPA license, and signed a cooperation agreement with the government to avoid criminal prosecution.

In cross-examination, Skilling defense attorney Randy Oppenheimer noted that setting reserve amounts was a subjective process -- and cited an internal Enron memo noting that the company, also in mid-2000, had taken too large a reserve in its attempts to safeguard itself against credit risk from customers unable to pay. But Colwell rejected the suggestion that the reserve adjustments were beneath notice or might somehow balance out, insisting that such "backward engineering" of reserves to meet earnings targets simply couldn't be justified.

Pressed by Oppenheimer -- who calmly concedes "fair enough!" when a witness pushes back at him -- Colwell did, however, acknowledge that neither Skilling or Lay had directly ordered him to do anything illegal. (The word of Skilling's desire to beat earnings by two cents, for example, had been relayed from another accountant.) And no, he never complained to anyone at Enron that he was being asked to do something wrong.

How much all this was connecting with the jury was unclear. There were a few yawns and glazed expressions on the faces of some jurors at various points during the day.

This continued to be the case into mid-afternoon, when Colwell gave up the witness box to Wanda Curry, a veteran former Enron accountant who had led an investigation into problems at Enron Energy Services, the company's highly touted retail business.

Curry was nervous on the stand, and she often retreated into the complex jargon of accounting and risk management. But she struck a chord early, when she testified about the reason she was given for being replaced as chief accounting officer at Enron North America, the job Colwell took over. Said Curry: "I was told I was being replaced because I was not capable of making aggressive accounting decisions."

Curry's primary role as a witness, in testimony expected to wrap up early Tuesday morning, was to describe the disaster that was EES, which she was assigned to investigate in late 2000, on a special assignment from Causey and Rick Buy, Enron's chief risk officer.

She recalled, for example, how a large tray crammed with hundreds of uncashed checks was discovered on the floor under a trader's desk in the retail division. This led to the revelation that California utilities owed EES $511 million that might never get paid. The division faced hundreds of millions more in trading losses. And Curry also led a "deep dive" investigation into the 13 biggest contacts the retail business had signed -- and discovered that the business and contracts were a mess, overvalued by $251 million. Her goal at EES, Curry testified, was "stopping the bleeding."

With the total list of unreported problems at more than $1 billion, Curry briefed Delainey ahead of an early April meeting he had scheduled with Skilling. Delainey had been moved in as CEO of EES to straighten out the division. It was the nightmarish prospect of having to tell investors that EES was really losing hundreds of millions that prompted Enron management to reorganize the division by stashing many of EES' key functions -- and much of the red ink -- inside the booming wholesale business, Curry testified. (EES instead reported a $40 million profit for the first quarter of 2001.)

Skilling defense lawyer Ron Woods confronted Curry with video of a 2004 deposition where she appeared to be saying the consolidation was justified for efficiency reasons. But Curry insisted she was speaking only of a small part of the business that was merged into wholesale, not the larger shift that took place -- nor the hiding of EES losses. By day's end, she was refusing to yield an inch, during increasingly testy questioning. That's when the judge called it a day, sending the jury home at about 4:30 p.m.

Monday's missing man was once again Ken Lay, whose name was barely mentioned during the testimony. In cross-examining Colwell, the Lay legal team took only two minutes, making just a single minor point. And with Curry on the stand, lead Lay attorney Mike Ramsey left the courtroom for the afternoon to see his dentist for a broken tooth.

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