The day before his death in the fog-shrouded Chinese city of Chongqing, Neil Heywood sensed that something was amiss.

The British businessman had been summoned on short notice to a meeting in Chongqing in early November with representatives of the family of Bo Xilai, the local Communist Party chief, according to an account by a friend whom Mr. Heywood contacted at the time. Mr. Heywood told the friend he was "in trouble."

After...