In the 16 months since the Sept. 11 attacks, thousands of Middle Eastern men have been questioned and detained by the FBI. Many Americans have wondered what became of these people. How many were actually terrorists? How many were actually rabid followers of Osama Bin Laden's jihad against America? One of them, Ali Saleh Kahlah Al-Marri — a 37-year-old from Qatar who returned to the United States on Sept. 10, 2001, less than 24 hours before the World Trade Center attacks — has become the target of a massive terrorism investigation. FBI agents first questioned Al-Marri at his West Peoria,...