Witnesses also saw McVeigh and another man prowling around federal buildings in Omaha, Neb., and Phoenix, Ariz. Using aliases, McVeigh and Terry Nichols, another army buddy implicated in the plot, had begun buying and storing tons of fertilizer, according to a government affidavit. Since neither man was farming at the time, the fertilizer was more likely to be used for building bombs than growing crops. Clearly, the plotters knew what they were doing, and may have planned to strike again if they had gotten away with the first attack. But if they were coldblooded, they were also amateurs who left a trail of telltale evidence for the Feds to follow.

In the month since the bombing, investigators have pieced together an outline of the plot that took 168 lives. Last week federal officials described their basic findings to NEWSWEEK. The bombing does not appear to be the work of an ingenious conspiracy fomented by a well-organized, well-financed extremist group. Investigators have dismissed a sinister foreign connection or a cabal of army commandos. Rather, they think they are looking at no more than a haft-dozen figures from the far-right fringe–perhaps as few as three or four. They believe that the plotters financed the bombing not by robbing banks, as earlier reported, but by selling (possibly stolen) weapons at gun shows. Some family members of the plotters, including wives and children, may be drawn in as witnesses, if not co-conspirators. Still many weeks away from wrapping up the case, officials haven’t ruled out a surprise or two. In the meantime, the FBI and the Justice Department are trying to squeeze the suspects into ratting on each other.

The first one arrested, Tim McVeigh, continues to stone-wall, calling himself a “prisoner of war.” McVeigh’s cunning and folksy lawyer, Steve Jones, is likely to keep McVeigh buttoned up. But earlier this month, The New York Times reported that McVeigh had been confiding in acquaintances while in jail. According to the Times, McVeigh admired to bombing the Murrah building, but claimed he had not known about the day-care center. Investigators are dubious; some suspect that McVeigh’s defense team concocted the story to test whether McVeigh might avoid the death penalty if presented in a less callous light. Terry Nichols has more of an incentive to talk. His lawyer, Mike Tigar, is distancing his client from McVeigh, claiming the two had a “falling-out” last February. With reporters, the flamboyant Tigar is all wounded innocence, protesting that Nichols was, in the days leading up to the bombing, just an ordinary family man who puttered around his house, fixing his roof and watching “The Lion King” with his children.

The most promising snitch is Fortier. When first questioned, Fortier proclaimed his innocence while standing outside his trailer in Kingman, Ariz., beneath a flag emblazoned with DON’T TREAD ON ME. But then agents began dropping by several times a day and following him, a common FBI ploy to unnerve potential suspects. Fortier began to look sunken and withdrawn, according to a friend. So when the grand-jury subpoena arrived two weeks ago, Fortier decided to reveal some of what he knows–but perhaps not all. He told of checking out the Murrah building with McVeigh, though he denied a role in the actual bombing. Fortier’s lawyer is negotiating with prosecutors, discussing the possibility of leniency in return for incriminating information about his right-wing comrades. The Feds have the additional leverage of threatening to charge Fortier’s wife, Laurie, who may also have known about the plot.

One of the enduring mysteries in the OKBomb case is the identity of John Doe No. 2. Someone who resembles neither Nichols nor Fortier accompanied McVeigh when he rented a Ryder truck in Kansas. Investigators wonder if JD2 may not have been an unwitting accomplice–conceivably, Terry Nichols’s 12-year-old son, who was visiting his father for Easter. (Though his lawyer and his mother say he never accompanied McVeigh.) The Feds also want to learn more from McVeigh’s sister, Jennifer, a true believer in the wacky conspiracy theories that apparently motivated the bombers. If there is a new twist in the case, suggests one official, it may come from Jennifer’s circle of hard-core friends.

Inevitably, critics question why the Feds could not have nipped the plot beforehand. Neighbors knew of the Nichols brothers’ penchant for bomb-building, and McVeigh tried to sell at least one undercover cop a rocket launcher that, he claimed, could be used to shoot down government helicopters. A former Detroit-area militia “intelligence chief,” Joseph Ditzhazy, told NEWSWEEK he had warned federal investigators more than a year ago about members of the Michigan Militia. Had the Feds followed up, he insists, they might have uncovered plotting by McVeigh and Nichols, who occasionally attended militia meetings. Officials dismiss Ditzhazy as an unreliable serf-promoter. Even so, as the FBI asks Congress for more resources to penetrate extremist groups, investigators will be increasingly dependent on informants whose reliability is suspect.

Fortunately, the Feds have other tools. For the past year, the ATF and the Army Corps of Engineers have been blowing up car bombs at the White Sands Proving Ground in New Mexico. The project, code-named DIPOLE MIGHT, is designed to create a computer model to unravel terrorist car- and truck-bomb attacks. By coincidence, an ATF agent assigned to DIPOLE MIGHT happened to be in Oklahoma City on April 19, working at the federal courthouse, which stands across the street from the Murrah building. He saw the devastation and called the ATF office in Dallas. The Murrah building had just been hit by an “anfo” (ammonium nitrate) bomb of at least several thousand pounds, he reported. Within minutes, explosives experts trained under DIPOLE MIGHT were dispatched to the scene. They identified the type and size of the bomb almost immediately. Identifying the murderers who put it there will take a little longer. The plot may not have been vast, but there were too many people in on the secret to keep it forever.