Robert Ludlum's The Bourne Sanction (Bourne Series #6)

After so many adrenaline-soaked years risking his life, Jason Bourne is chafing under the quiet life of a linguistics professor. Aware of his frustrations, his academic mentor asks for help investigating the murder of a former student by a previously unknown Muslim extremist sect called the Black Legion. The young man died carrying information about the group's terrorist activities, including an immediate plan to attack the United States. In Europe, Bourne's investigation of the Black Legion turns into one of the deadliest and most tangled operations of his double life-the pursuit of the leader of a murderous terrorist group with roots in the darkest days of World War II.