By Joby Warrick, Washington Post

He was known to the CIA's clandestine service as "the chemist," and few at headquarters would ever know his real name. A professor and a gifted scientist, he had been perfectly positioned for spy work, with a job that entitled him to privileges not accorded to ordinary Syrians, including a broad latitude to travel and to meet with foreigners in the crowded souks and smoke-filled cafes of the old city.