Three months ago, it wasn't at all clear that Congress's attempt to probe the intelligence community's handling of pre-Sept. 11 information would yield many insights. The staff director of the newly formed Joint Inquiry Committee had been asked to leave. Arguments between the panel and intelligence agencies over what could be declassified were painfully slow. Even lawmakers were worrying out loud about its direction.

But the public hearings that began last week put those worries to rest. Filled with new details and compelling testimony by FBI and CIA agents, the panel staff, toiling behind closed doors, created a roadmap that undoubtedly will be the jumping-off point for the more thorough, independent commission that Congress, family members of those killed in the attacks and now even President Bush are endorsing.

The star witness in the turnaround, said lawmakers and their staff members, is an attorney with an understated style and a decades-long track record as an aggressive, evenhanded investigator. For hours at a time, Eleanor Hill, a former Pentagon inspector general, has calmly and painstakingly walked the lawmakers through a maze of international plots, subplots and breathtaking missed opportunities leading up to the fatal terrorist attacks.

"She's framed the issue in a noninflammatory way," Rep. Jane Harman (D-Calif.) said yesterday as she walked in front of a blackened screen set up in the hearing room to conceal the identities of three FBI agents testifying. "Eleanor Hill coalesced a competent staff to create a roadmap for reform we've been looking for. She's the one. She's the leader."

In a brief interview yesterday as she worked her way through a Capitol Hill basement salad bar line, Hill said one simple but daunting challenge was to assemble "the volume of stuff we've had to look through" and to "put it together in a readable form, in a form that would tell the American people a story."

The panel staff, working in offices at the CIA, FBI, National Security Agency and other intelligence-gathering agencies, combed through 400,000 pages of documents and zeroed in on nearly 7,000 pages to form the narrative stories their three reports have told about the clues available before the attacks, the hijackers' trail and the valiant but vain efforts by individual CIA officials and FBI agents to make their bureaucracies move faster.

Big, complex investigations happen to be Hill's forte.

As a federal prosecutor in the U.S. attorney's office in Tampa, and the first woman employed in that office, Hill never lost a case. Hired by then-Sen. Sam Nunn (D-Ga.) for the Permanent Subcommittee on Investigations for the Senate Governmental Affairs Committee that he chaired, Hill spent 15 years probing organized crime, the Teamsters, mismanagement in the federal student loan program, fraud in trade schools and lavish expenditures by some Blue Cross Blue Shield plans. She ran one set of hearings about the plans just two days before she gave birth to her son.

Hill also served, in 1987, as Nunn's special counsel during the Iran-contra hearings investigating the secret sale of arms to Iran in exchange for help in freeing American hostages in Lebanon.

In 1995, President Bill Clinton nominated Hill as the Defense Department's inspector general. She went from heading an office of 10 highly motivated Senate staffers to leading a demoralized group of 1,500 defense investigators who were facing a one-third cut in their office's positions.

David Buckley, Hill's former special assistant at the Pentagon, said the key to her success is that she "collects all the facts and assesses the situation before coming to a conclusion. Even though she's an extremely compassionate and nice person, she doesn't let her emotions pull her away from the facts."

She led the joint CIA-Defense Department review of allegations that the CIA failed to share with Congress information it had that one of its agents, a Guatemalan colonel, had been involved in the killing of a Guatemalan rebel married to an American lawyer.

While at Defense, Hill set up an Office of Intelligence Review to review intelligence operations at an inspector general's office that had focused most of its attention on waste, fraud and abuse.

Her management style, said Judith Miller, the Pentagon's former general counsel who worked with Hill there, "is not to micromanage everything. She trusts her people."

Nunn, Hill said yesterday, taught her many things. Among the most unforgettable, she said, was this: "Congress has a tremendous power to investigate, and a tremendous responsibility to exercise that power fairly and accurately. You don't want to abuse it. You want to do it accurately."

The closest she has come to uttering a personal, and slightly emotional, judgment of the mounds of classified papers documenting the determination of Osama bin Laden and al Qaeda to harm Americans, was when she seemed to be thinking out loud in a room full of reporters the day before the hearings began: "You keep reading it over and over again. It's very serious stuff. Nobody enjoys reading over and over again about the types of threats that come in about this country."

Still, she insists, the toughest part of the job has been "to explain to my 9-year-old son why I missed his baseball game." Hill tried, she said, but he was unimpressed. So she arranged for him to attend the first public hearing and watch his mother hold forth before senators, House members and a gaggle of photographers and reporters.

Did she win him over? Not by a long shot. She promised to get to the next baseball game.

Eleanor Hill has a decades-long track record as an aggressive, evenhanded investigator.