By October 1973 special prosecutor Archibald Cox was tracing the Watergate cover-up to the Oval Office. President Nixon demanded that he stop. In the "Saturday Night Massacre" two heads of the Justice Department quit before Nixon found a subordinate (Robert Bork) willing to fire Cox. Immediately public opinion swung against the president and turned Cox into a hero--seemingly Washington's last honest man.Cox's life was distinguished well before that Saturday night. He had been a clerk for the legendary judge Learned Hand, a distinguished professor at Harvard Law School, and the Solicitor...