Robert Ludlum's The Bourne Legacy (Bourne Series #4)

Jason Bourne, international assassin of deadly repute, was an identity assumed by covert agent David Webb. Retired from the CIA and now a professor at Georgetown University, Webb's life is finally his own. His newfound calm is shattered when he becomes the target of an assassin and is framed for the murder of his two closest associates—the only ones who knew the full truth about Bourne. Fighting for his life against unseen assailants, the Bourne identity asserts itself and Jason Bourne is once again in control.