Canadian authorities questioned Slahi, sent officers to his mosque, and put a police car on his tail. One night, Slahi later said, he was awoken by agents drilling holes into his third-floor apartment to plant surveillance cameras. He called the local police station, saying his neighbor was spying on him; the police suggested he cover the holes with glue.

"It was very clumsy," Slahi later said, "but they wanted to give the message that 'We are watching you.'" He moved to a room at the mosque, but the surveillance continued.

Tired of constantly having "people right behind me, at the market, watching my butt," Slahi decided to return to Mauritania. The FBI tracked his itinerary: flying via Brussels to Dakar, Senegal, where his brothers were to pick him up for the 270-mile drive north to Nouakchott, the Mauritanian capital.

At Washington's request, Senegalese police arrested Slahi when he landed. He was questioned about the Millennium Plot and his jihadist past, but denied everything. Four days later, the Senegalese put Slahi on a private plane to Nouakchott, where he was arrested again.

An American team came to interrogate Slahi. He continued to deny wrongdoing, and after three weeks the Mauritanians released him. "The Americans keep saying you are a link," Slahi later said Mauritanian officials told him. "But they didn't give us any proof, so what should we do?"

After 9/11, American agents went back to question Slahi in Nouakchott. One struck him with a plastic water bottle and threatened torture, Slahi said. The next month, Mauritanian intelligence called Slahi in for more questions.

Why not flee?

"Maybe I'm stupid, I don't know," Slahi later said. "I went to the police and said, 'Why do you want me?' They said, 'Please don't worry, it is just formalities.' "

After a week in jail, however, he learned he was being sent to Jordan. This was disturbing, Slahi thought, because "the Jordanians have [a] very bad reputation when it comes to treatment of detainees."

"Can you turn me over to the United States?" he asked. "What do I have to do with Jordan? Turn me over to America."

"The United States wants you to be turned over to Jordan," he was told.

"Then, man," Slahi said, "what happened to me there is beyond description."

Jordanian agents pressed him on the Millennium Plot. One "struck me twice in the face on different occasions and pushed me against concrete many times because I refused to talk," Slahi said. "He threatened me with torture" and pointed out another prisoner, "this guy who was beaten so much he was crying, crying like a child." As the months dragged on, Slahi said, he lost so much weight that he looked "like a ghost."

In July 2002, U.S. agents showed up to retrieve him.

"They stripped me naked like my mom bore me, and they put new clothes on me," Slahi said. Aboard the plane, he was chained in place and fitted with a diaper. "I had to keep my water for eight hours straight," he recalled. "Psychologically, I couldn't [urinate] in the diaper. I tried to convince myself that it was okay, but I couldn't and I was exploding [on the inside]."