Lawrence Walsh took a seat in the living room of his Nichols Hills home and glanced at the Dalmatian trailing after him. The man grinned wryly, explaining that he had just swiped the dog's favorite chair. As a conciliatory gesture, the 85-year-old Walsh rubbed behind the dog's ears while Walsh's wife, Mary, chatted on the phone in a nearby room.The scene of domestic tranquillity was belied by piles of newspaper clippings and government documents in the adjoining dining room, reminders of Walsh' years spent as the independent prosecutor investigating the administration of former President Ronald Reagan.For seven years, Walsh led the criminal probe of the covert White House operation that illegally sold arms to Iran in exchange for the release of U.S. hostages.In turn, those profits were diverted to resupply the anti-communist contra rebels in Nicaragua, even though Congress had banned such aid.Walsh, a life-long Republican, former federal judge and U.S. deputy attorney general under President Eisenhower, has revisited that tumultuous period in "Firewall: The Iran-Contra Conspiracy and Cover-up," a 544-page book published by W.W. Norton & Co."It's like going back over an unpleasant experience, to some extent," said Walsh.That might be an understatement. Appointed as the Iran-Contra independent counsel in December, 1986, Walsh railed against a seemingly impenetrable White House bureaucracy while he lived out of a suitcase -- commuting between his hometown of Oklahoma City and the Watergate Hotel in Washington, D.C. -- and endured blistering attacks from his fellow Republicans.The investigation ended in frustration. Government officials whom Walsh had targeted for investigation prevented him from gaining potentially incriminating evidence by labeling the material classified. And members of Congress -- eager to hold hearings on the scandal -- granted immunity to key Iran-Contra players such as fired White House aide Lt. Col. Oliver North and former national security advisor John Poindexter.Walsh conceded he hurried through parts of his investigation so his prosecution would not be tainted by North's protected Congressional testimony."It was almost impossible, but we went through with it by closing our ears to it and by telling witnesses not to tell us what they learned [from the hearings]," said Walsh."It put us at a tremendous disadvantage. The witnesses all knew what North said, and we didn't. A hostile witness doesn't tell you things voluntarily. He only tells you things that he thinks you already know. When he knows that you don't know what North says, he's got the advantage over you."The independent prosecutor won convictions against North and Poindexter, but they were overturned when a federal court determined it was impossible to tell what witnesses had gleaned from the Congressional hearings.Another blow to Walsh came on Christmas Eve, 1992, when President Bush pardoned ex-Defense Secretary Caspar Weinberger, who was facing trial for perjury and obstruction of justice."It was such an open cover-up," Walsh said of the pardons. "Obviously, there was no other reason for it. It seemed unwise for him (Bush) to spoil his standing by doing that. You have to be angry, but I think I was more disdainful than angry."In "Firewall," Walsh finds plenty of blame for what went wrong with the investigation and does not exclude himself. He said he might have erred by being too soft on the Reagan administration. Instead of slapping White House officials with subpoenas, he opted for the less-contentious route of requesting information."I figured if I subpoenaed thousands of documents, I'm going to get into litigation with the government," Walsh said."They've got lawyers that could have dragged it out ... and I had to get those documents into my files before North testified."The probe dragged on, anyway. And Walsh was never able to prove Reagan knew the arms sales to the Ayatollah were illegally funding the contra rebels. Walsh said he could not break through the "firewall" that White House aides had created to let the president claim ignorance."[Reagan] knew enough to be culpable," Walsh said."He had to have some reason for keeping this otherwise non-productive activity going."After all, the arms-for-hostages deal was no success, having resulted in only one hostage being released. Walsh finds it unfathomable that North, Poindexter and their cronies would have continued the operation without approval from Reagan."There were too many people too intelligent to have gone through this activity for so long if they didn't think they had the president's backing," Walsh said. "Poindexter's backing alone would not be enough."These days, Walsh is grateful to be out of the national limelight. He said he sympathizes with Whitewater independent counsel Kenneth Starr, whose probe of the Clinton administration seems to have stalled."He was given the job and had to do it, but the statute was too broad," said Walsh."The [independent counsel] law should be shrunk. An independent counsel shouldn't be required for anything except the misuse of federal power. It should be applicable only to events that occur in office and events of public interest."