When Rachel Ehrenfeld, author of the book "Funding Evil: How Terrorism Is Financed and How to Stop It," opened her apartment door just before 10 p.m. on March 3, she believed she was simply receiving some legal papers from London. But this was no ordinary messenger. According to Ehrenfeld, the visitor carried a warning as well: "You had better respond. Sheik bin Mahfouz is a very important person, and you really ought to take very good care of yourself.” "I expected to receive some legal papers, not a threat from a Saudi sheik in my own country,” Ehrenfeld told me...