THE GRILLING BEGAN IN MIDAFTERnoon, but former President Roh Tae Woo did not start talking until around midnight. Yes, he had taken money from the chaebol, South Korea's huge conglomerates. No, he insisted, his $650 million slush fund did not come from bribes. They were merely "political donations." The prosecutors begged to differ: their investigation, including the questioning of 36 top chaebol executives, yielded evidence that Roh had provided favors in exchange for payoffs.

The next day prosecutors obtained an arrest warrant that alleged two specific cases of bribery: one involving international conglomerate Daewoo and the other the construction company Dong Ah. At 7:30 p.m. Roh emerged from the prosecutor's office on his way to Seoul's detention center--unhandcuffed in deference to his station. He stopped in front of a crush of journalists. "I am truly sorry," he said. "I take full responsibility, and I'm ready to accept any punishment willingly." Then in a gesture to the big companies that lavished funds on him, Roh added, "I seek your understanding so that we will not be hurt in international competition."

Roh's contrition did little to blunt his countrymen's rage. In a tearful press conference last month, the retired general admitted that he had controlled a $650 million secret fund as President from 1988 to 1993 and had kept $221 million for his own use. Ever since, the public has been pressing to know who donated the funds, why they did so and where the millions were spent. Most of all, they want the head of Roh, the man who helped restore democracy in South Korea and who in his presidential days liked to claim he was just an "ordinary" man who stood for a clean political system.

Few South Koreans ever really believed Roh was clean, but most were staggered by the sheer immensity of his greed, as well as the long reach of his money. Opposition firebrand Kim Dae Jung has admitted that he accepted a $2.6 million "gift" from Roh, his enemy, and he has accused President Kim Young Sam of accepting even more, a charge the President denies. A party colleague of Roh's until the general's retirement in 1992, President Kim is under pressure to put investigators on the trail of Roh's political payouts. Says Dr. Kim Kyo Jun, a surgeon at Kum Kang General Hospital in Seoul: "Even if the President has to grant a massive amnesty to all those involved, every detail of the crimes committed has to be revealed for the sake of the nation."

For the moment, the investigation is focusing on the basics. Prosecutors have 20 days to indict Roh, whom they placed in detention after his arrest because of "the danger of the accused's destroying evidence." So far, Roh has refused to explain who specifically contributed to his slush fund or where the money went. To hunt down the answers, Seoul obtained Switzerland's cooperation to search Roh's accounts there, and prosecutors are looking for at least $42 million in real estate investments they believe Roh made in relatives' names. The day after Roh's arrest, prosecutors also busted Lee Hyun Woo, a retired general, Roh's chief of security and the confessed manager of part of the slush fund.

Treading more softly where the chaebol are concerned, prosecutors reportedly might recommend that only suspended sentences be handed to the businessmen involved. "There was a tradition and atmosphere that the chaebol were under a vague threat to give," says Yang Song Chul, a political scientist affiliated with Kyung Hee University. "They should be treated as lightly as possible." But the prosecutors appear determined to find out who gave what. In Roh's arrest warrant, for example, they said that Daewoo chairman Kim Woo Choong bribed Roh with $14 million in exchange for a lucrative contract to build a submarine base.

By far the most explosive dimension of the case involves the political funds. Though Kim's ruling Democrats officially favor a full investigation, they are not eager for it. Kim prefers to stress his own effective anticorruption measures since he took office and his pledge not to take one won from business interests--a promise that is widely believed. As long as investigators do not try to learn whether other politicians took money, the President will face accusations of a cover-up. Kim Dae Jung has promised "all-out war," and 77% of respondents in a recent newspaper poll want a full accounting of the political funds. "This is a step forward for Korean democracy," says Kang Tae Hoon, a political science professor at Dongkook University, "because now everyone knows that even if a President does something wrong, he can be arrested."

The man who learned that the hard way is languishing in the Seoul Detention House. His car was pelted with eggs and rocks as it reached the facility, 30 minutes south of Seoul. Roh was shown to a 12-sq-m cell equipped with a small TV set (two hours a day only, after dinner), a sleeping platform, three blankets and a futon. There is no heat, apart from a small coal stove in the corridor outside, and Roh wears the standard white prison uniform. It's an austere life, but accused felons don't usually have it even that good.

--With reporting by Stella Kim/Seoul