WASHINGTON — Still hidden in secret grand jury transcripts and locked prosecutors’ files is the dramatic story of how the Watergate case was broken We have spent weeks interviewing FBI sources, government prosecutors and defense attorneys to get the details that never came out at the public hearings. The real heroes of Watergate, we have concluded, were the FBI agents who wouldn't let the White House obstruct their investigation and the orginal Watergate prosecutors who painstakingly fitted the jugsaw pieces into a criminal conspiracy The three unsung prosecutors — Earl Silbert, Seymour Glanzer and Donald Campbell — handed the case on a silver platter to the special prosecutor and his staff of 90 They had no way of knowing in June, 1972, that President Nixon personally had issued the order to cover up the trail of break-ins, bag jobs, forgeries, frame-ups, rough-ups and buggings, which we now know as Watergate. The FBI agents, therefore, en countered incredible obstacles from the moment they started down the Watergate trail. The key witnesses either lied outright or witheld vital information. As an example, the G-men for weeks couldn't identify the two chief culprits, G. Gordon Liddy and E. Howard Hunt, who were known to them only as George Leonard and Ed Warren The notorious pair were well known, of course, inside the White House, which paid them blackmail to lay low. The CIA, which provided the phony identities, also knew them. Late in the morning of the Watergate arrests, Liddy sought out then-Attorney General Richard Kleindienst on the Bur ning Tree golf course. Thus, the Attorney General actually met one of the ringleaders whom the FBI was seeking On July 6, the CIA finally delivered a memo to the acting FBI director, Pat Gray, revealing that Liddy and Hunt had been furnished false identities. Yet Gray locked the memo in his safe, without breathing a word of it to his own agent. Not until November, 1972, did the prosecutors learn the true identities of George Leonard and Ed Warren. And it was April, 1973, before they found out about Liddy's meeting with Kleindienst on the golf course. Meanwhile, John Dean telephoned Gray from the White House daily to find what progress the FBI was making. On several occasions, Dean slipped through a private door in Gray's office to pick up FBI teletypes, transcripts and raw reports on the Watergate investigation. Dean also prepared White House witnesses for their FBI interviews and then sat in on the questioning. And for awhile, he was permitted to attend interviews that the prosecutors conducted. The prosecutors also gave their superior, Assistant Attorney General Henry Peterson, progress reports. He passed on the key developments to Dean and, sometimes, to the President himself. Thus, the White House knew every step the prosecutors were taking and, therefore, could keep ahead of them. But the President's men did not reckon with the determination of a judge named John Sirica, the diligence of the press nor the doggedness of the prosecutors and G-men. Waterbugger James McCord, under threat of a long prison term, was the first to break. When one of the White House con spirators, Jeb Stuart Magruder, received a lofty new appointment, McCord com plained bitterly to John Dean: ‘‘I'm going to prison and Magruder’s getting his pic ture in the papers. To save himself, McCord began to spill what he knew. The prosecutors im mediately summoned Liddy, who was tight lipped as ever about his Watergate role. But they deliberately detained him and engaged him in idle conversation. This generated alarmed whispers inside the White House that the un predictable Liddy was talking. A panicky Magruder flew to Bermuda in search of a lawyer who had been recommended. And the President dispatched Dean to Camp David to write a Watergate report. The cool, calculating Dean suspected the President was setting him up. For if Dean committed the White House cover story to wrn.... we might make himself the prime scapegoat. He, therefore, put nothing on paper. Instead, he telephoned his lawyer, Thomas Hogan, from Camp David. Hogan recommended an able trial lawyer, Charles Shaffer, who met them secretly in an out-of-the-way apartment in the Washington suburbs. It took Dean seven hours to summarize the conspiracy. “It has to end,”’ he concluded. “I'm ready to end a ‘Don't run into the machine guns yet,”’ Shaffer advised. He sought out the prosecutors to see what kind of a deal he could make. The chief prosecutor, Earl Silbert, refused to grant Dean immunity. Arrangements were made, nevertheless, for Dean to tell his story so the prosecutors could judge what kind of a witness he would make There followed a series of secret meetings with the prosecutors, sometimes lasting most of the night in Shaffer’s Rock ville,Md., office. Magruder, meanwhile, tried to lie to his lawyer, James Sharp, who finally told him bluntly: ‘‘Jeb, pretty soon you're going to have to tell me the truth.” When Magruder finally told the truth, Sharp advised him: ‘Jeb, you've got no choice. We should go to the prosecutors and make the best deal we can.” One by one, Silbert hauled the wit nesses before the grand jury. Before he was finished, the Watergate case had been cracked.