Was the illegal diversion of profits from Iranian arms sales to the Nicaraguan contras an unauthorized plot hatched by a small band of zealots in Ronald Reagan's National Security Council? Or did high-ranking members of the U.S. intelligence community not only learn about the scheme and do nothing to stop it, but unlawfully help to conceal it from Congress?
Those unsettling questions have become the focus of the investigation by Lawrence E. Walsh, who has been the Iran-contra independent counsel since December 1986. His inquiry is being assisted by Alan Fiers, former head of the CIA's Central American Task Force, who...