He was chained by one hand to the wall in a windowless cell and left with a bucket and a bottle in lieu of a latrine. He remained there for nearly a week, he said, and then was blindfolded and bound again and taken to another prison. "There, they put me in a room, suspended me by my arms and attached my feet to the floor," he recalled. "They cut off my clothes very fast and took off my blindfold." An older man, graying at the temples, entered the room with a young woman with shoulder-length blond hair, he said. They spoke English, which Mr. Saidi understands a little, and they interrogated him for two hours through a Moroccan translator. At last, he said, he thought he would learn why he was there, but the questioning only confounded him.

He said the interrogators focused on a telephone conversation they said he had had with his wife's family in Kenya about airplanes. But Mr. Saidi said he told them that he could not recall talking to anyone about planes.

He said the interrogators left him chained for five days without clothes or food. "They beat me and threw cold water on me, spat at me and sometimes gave me dirty water to drink," he said. "The American man told me I would die there."

He said his legs and feet became painfully swollen because he was forced to stand for so long with his wrists chained to the ceiling. After they removed him from the chains, he said, he was moved back to the "dark" prison and a doctor gave him an injection for his legs.

Image Laid Saidi was seized while running an Islamic charity in Tanzania in 2003. He said he lost his Algerian passport and used a false name on his Tanzanian residency permit, above. Credit... Samantha Appleton for The New York Times

After one night there, he was moved to a third prison. He said the guards in this prison were Afghans, and one told him that he was outside Kabul.

There were two rows of six cells in the basement, which he described as "filthy, not even suitable for animals." Each cell had a small opening in the zinc-clad door through which the prisoners could glimpse one another as they were taken in and out of their cells. At night, they would talk.