ate one evening last summer, Saad Eddin Ibrahim, a prominent Egyptian-American civil rights advocate and one of the Arab world's leading social scientists, was working in his study - a spacious one, on a quiet, tree-lined street in the suburb of Maadi, one of Cairo's most fashionable neighborhoods. The room was bursting with books, stacks of papers, family photographs and half-finished cups of tea. On that particular evening, the 61-year-old professor of sociology was alone in the house: his American-born wife, Barbara, was out of town; his son, Amir, was out with friends; and his daughter, Randa, was at her own home with her husband and Saad Eddin's second, recently born grandchild. It seemed unusually quiet, the professor thought to himself. Evening prayers had recently ended at the adjacent Victory College mosque, and the worshipers had left. With their departure, all noise, all sounds, seemed to have come to an end.

A partly bald and bearded man of medium height and build, and an outspoken proponent of his views, he ensconced himself on the sofa and began to read. He may have fallen asleep, or simply been deep in thought; he can't quite recall. Whichever it was, he gradually became aware of a persistent drumlike pounding on his front door. Sleepily, he made his way down to the entrance foyer, opened the door and was abruptly jolted completely awake. A dozen armed guards from State Security Investigation, or S.S.I., stormed into the house, as 40 or so others cordoned it off. Some raided his study and eventually carted off scores of boxes of files and books, his computer - and the family safe. Others surrounded him. "Come with us," one of them said. "Come with us. You're under arrest."

"I looked out of the door," Saad Eddin said a few weeks ago, as we sat in the open-air cafe of my Cairo hotel one late April afternoon. "It was like the siege of Stalingrad. Armored cars surrounded the house. Guards were posted everywhere. Why had so many people come to arrest one harmless intellectual? Why didn't they just make a phone call? I would have come."

It was a little before midnight when Saad Eddin Ibrahim was bundled into an armored car and driven about three miles, high above Cairo, into the Mokattam Hills to the Ibn Khaldun Center for Development Studies. Established by Saad Eddin 12 years before - and named for the great medieval Islamic scholar - the center had emerged as a leading exponent of democratic reform and intellectual freedom in the Arab world.

As the armored car continued to climb the sinuous mountain road, Saad Eddin glanced out of the window. "I could see the whole motorcade," he said. "There were at least 10 cars ahead of me and another 10 behind: bright lights in the darkness. There are so many layers, so many conflicting images, in all of this, and it was that night that I first saw the contrast, the physical part - two starkly different images, one romantic, one harsh. Caravans in the desert, I thought, as I looked at the twinkling lights, or the carts of death, during the French Revolution, taking their victims to the guillotine."

It was June 30, the last day of the fiscal year, and Nadia Abdel Nour, the financial manager of the Ibn Khaldun Center, had worked late that night supervising the closing of the books. A genteel, attractive woman of 50 or so, with luminous dark eyes, she is a Sudanese refugee and the sole support of her large refugee family. At around 8 p.m., as she waited at a nearby bus stop, her neatly ordered world began to fall apart.

"They grabbed me from behind, blindfolded me, threw a bag over my head," she later said. She had no idea who they were. She was terrified. "I thought I was being kidnapped!" she said with a shudder.

"When we arrived at Ibn Khaldun, I found her there," Saad Eddin said. "She was outside the center. She was sobbing and shaking. She was still blindfolded. She had no idea where she was, or why."

As Saad Eddin and Nadia Abdel Nour watched in bewilderment, dozens of S.S.I. officers began tearing the Ibn Khaldun Center apart. Others surrounded the building, blocking all access roads. Still others took up positions around it, their automatic assault weapons drawn. Many of their faces were partly concealed by visored helmets, and it was impossible to know who they were.

All across Cairo that evening, lawyers and economists, students and social workers were arrested and taken off to high-security prisons. By the following week, 28 officials and employees of the Ibn Khaldun Center, along with representatives of the League of Egyptian Women Voters, had been swept up. Most remained in prison for two months. During that time, not one of them - not even Saad Eddin Ibrahim - was charged. They were held under Egypt's draconian emergency laws, which President Hosni Mubarak has renewed every three years for the 20 years of his presidency.

It was nearly dawn when Saad Eddin Ibrahim and his 20-car security escort were ushered through the gates of S.S.I. headquarters -- where he was held through the following night. For 14 hours, Saad Eddin was interrogated about his work, his public lectures and his dozen or so books. Interrogators came and went from the windowless spartan room. Some were from the office of the public prosecutor, others from S.S.I. After that ordeal, he was transferred to the high-security section of the Tora prison complex in South Cairo, one of the country's most dreaded detention sites. He would spend six weeks there before being released on bail.

"My first interrogation ended at about 8 o'clock that night," Saad Eddin said. "It was just twilight when I arrived at Tora Mazra'at. An elderly, white-haired police corporal was sitting at a desk. He peered at me over his half-glasses: 'Dr. Saad Eddin Ibrahim?'

"I thought he was reading a newspaper, but it was too early for that, and then he said: 'I'm Ali Hamdan. I was a private here 20 years ago, when you came to do research. It was a long time ago.' He paused for a moment and then he asked, 'What has happened to the world?'

"I saw the human face of Egypt that night in this old man," Saad Eddin said. "Previously, I had seen the brutal face of the state. There have been so many faces of Egypt in all of this, so many threads. There I stood in handcuffs, and I had to comfort this old man."