What is the main conflict in The Bourne Ultimatum by Robert Ludlum?

The Bourne Ultimatum is a novel about the complex machinations of Cold War intrigue. It begins with the discovery by Carlos the Jackal that his old nemesis, Jason Bourne, was not killed thirteen years ago in Hong Kong, as had been widely publicized. In fact, he is living in Maine as David Webb, a university professor. Carlos, fed by his hatred for Bourne, whose existence had clouded his self-proclaimed title of the "world's greatest assassin," fires the first salvo in a murder attempt against David's friends and mentors, Alex Conklin and Dr. Morris Panov. David immediately fears for the safety of his family and allows his alter-ego of Jason Bourne, cold blooded killer, to emerge. The novel deals with their conflict culminating in the surprise death of Carlos, the Jackal.