What is the main conflict in The Pelican Brief by John Grisham?

After a consummate professional assassinates two Supreme Court justices, the surviving justices, the FBI, the CIA, the White House, a law professor in New Orleans, and his beautiful, brilliant student/lover, look for a motive. Darby Shaw discovers the link, which she describes in the "pelican brief," which kills those who know about it, but is ultimately published and brings the mighty down.