It has to be one of the most bizarre--and chilling — of lost and found, certainly in the history of America’s nuclear program. Last week, after sheepishly revealing that a top-secret nuclear-weapons lab had lost a couple of computer hard drives that could help terrorists blow up an American city, the Department of Energy suddenly announced that it had found the little devils — incredibly, behind a copying machine. THE RELIEF AT the much-beleaguered DOE was palpable, but the mystery — and the danger — remain. In their desperate hunt for the missing hard drives, investigators were sure they had searched the secure area around the copying machine before and found nothing. The inescapable conclusion was that someone had sneaked back and left the hard drives where they could be conveniently discovered.

But who? And why? There is no doubt that the hard drives would be a prize for enemy spies and terrorists. They are nuclear-weapon how-to manuals, prepared by the government’s Nuclear Emergency Search Team (NEST), a sort of super bomb squad that can be sent at a moment’s notice to the scene of a nuclear-weapon accident or to disarm a missing or homemade nuclear device. Designed to “plug and play,” the hard drives can be popped into an ordinary computer and opened without a secret password. The information on them is not encoded. In the wrong hands, they could help terrorists navigate around a fail-safe system known as PALS, used to lock American nukes so they can’t be exploded accidentally or by thieves. Worse, the hard drives contain information that would help terrorists unlock a Soviet nuclear weapon, which is more likely to be floating around the black market than an American one. Or the information on the hard drives could be used to booby-trap a nuclear device to keep it from being disarmed. No wonder the hard drives are supposed to be safely guarded. Superficially at least, the security precautions at Los Alamos National Laboratory appear right out of “Mission: Impossible.” Simply to get through the lab’s perimeter gate, a visitor must wear a photo ID, punch in a PIN and submit a hand-print for verification by a high-tech scanner. The hard drives are kept in a vault maintained by the supersecret X Division, the most sensitive branch of the nuclear-bomb-designing lab. Roughly the size of a pack of cards, the hard drives are locked into “grab and go” kits, steel-reinforced suitcases that NEST members can pick up on their way to an emergency. Only 86 people had access to the vault, and only 26 of those could come and go without a full-time escort. A guard sits in the vault and monitors all visitors.

Before disappearing, the hard drives were seen at a NEST training exercise in early April. On May 7, as an out-of-control forest fire in the mountains around Los Alamos threatened the lab, someone on the NEST decided to remove one of the grab-and-go bags for safekeeping. The team member dialed open the combination lock on the suitcase to make sure everything was in place, and discovered that the two hard drives were missing. Despite a massive and obvious breach of security, the NEST told no one. For two weeks, the raging fires forced the lab to be evacuated, so the team didn’t get back into X Division until May 22. Searching furiously for the missing hard drives, the NEST found nothing. Finally, on May 31, the director of the Los Alamos Lab, John Browne, was brought into the loop, along with the lab’s counterintelligence chief — about three weeks later than he should have been. Chagrined officials from the lab and their bosses at the Energy Department were hauled before a congressional committee for a ritual flaying. Los Alamos is already in disrepute for allowing one of its X Division scientists, Wen Ho Lee, to download vast amounts of classified nuclear-weapons data from a secure computer at the lab to an unsecure computer at home. Lee was at one point suspected of spying for the Chinese, but was charged only with misusing secret documents; he has maintained his innocence throughout.

Inflamed by further security lapses, lawmakers last week acidly inquired: how could it be that the nation’s most-secret nuclear-weapons lab appears to use less-stringent rules for signing out material than most local public libraries? The charge was a bit of a cheap shot: visitors to the secret vault in X Division do have to sign in and tell the guard if they wish to take anything out. But they don’t have to actually check out material as they leave. This loophole may have been abused by lab personnel. Investigators say that some lab scientists regard security measures as bureaucratic nuisances.

There could be a benign explanation for the sudden reappearance of the hard drives last week. Possibly, a NEST member wanted to work on the hard drives on a computer in his office or at home. Ignoring the lax rules, he failed to sign for them. He was planning to return them to the vault, but the fire intervened. Afraid of getting caught with nuclear secrets — and transformed into another Wen Ho Lee, hounded by prosecutors and the press — the scientist panicked and kept mum when the search began. When no one was looking, he dropped the missing disks behind the copying machine to be found by investigators.

The more sinister explanation is that a NEST scientist stole the hard drives, made copies and gave them to who knows which forces of evil. The FBI is treating X Division as a crime scene. At least 10 NEST members have been given lie-detector tests, and three have reportedly flunked. The FBI is now examining the hard drives for evidence of copying or tampering.

At a minimum, the scandal of the missing hard drives will ruin careers and invite further security crackdowns. Energy Secretary Bill Richardson, who supervises Los Alamos, is not likely to become Al Gore’s running mate. The scandal points to the difficulty of controlling secrets in an age of instant communication. Both the State Department and two branches of British Intelligence have been embarrassed by losing laptops crammed with secrets. In one notorious episode, a James Bond-in-training for MI-6 apparently got drunk and left his laptop in a taxi. One can only hope that the story of the missing NEST hard drives will in the end be similarly diverting — and not terrifying.