The cleaning woman, Tracy Brockway, 32, was having an affair with the leader of Project 7 in a house bristling with 35 guns and thousands of rounds of ammunition, the sheriff said. He identified the militia's leader as David Earl Burgert, 38, whose last known job was renting snowmobiles, who could often be heard carping about judges on a local right-wing radio station and who has a long history of being annoying. At Christmas, when his neighbors lined streets with paper bags containing lighted candles, Mr. Burgert mounted his snowmobile and snuffed them out.

"If you picture a schoolyard bully who has a big mouth, that would be Burgert," said Bruce Parish, a detective in the sheriff's office.

David Earl Burgert, 38, was identified as the militia's leader.

This far northwest corner of Montana, along with the nearby northern neck of Idaho, has for decades been incubating right-wing militias, conspiracy theorists and white supremacists. Many of them have demonstrated an outsize appetite for military hardware and survival gear.

Kalispell (population 17,000) might seem an unlikely staging ground for militias bearing grudges. It is the county seat of Flathead County, one of the fastest-growing communities in Montana and a pristine outdoor destination that includes half of Glacier National Park and more than a million acres of mountain wilderness. The town is near the northern end of Flathead Lake, the largest freshwater lake in the West and one of the cleanest lakes in the world.

Yet a decades-old decline in an economy based on logging and mining, combined with the rise of a New West culture dominated by affluent professionals and retirees who go outside not to work but to recreate, has left many local people confused, resentful and looking for someone to blame. Project 7 appears to have set a new standard, both for zany scapegoating and for industrial-strength firepower.

"This is the weirdest, most violence-prone thing we have seen in Montana for a long time," said Ken Toole, a Democratic state senator who runs the Montana Human Rights Network, which studies right- wing movements in Montana and Idaho. "There is a comic element to these people," Mr. Toole said. "But it washes away pretty quickly because of the guns."

The Federal Bureau of Investigation and the Bureau of Alcohol, Tobacco and Firearms are taking it all seriously.

On Friday, after a long meeting with the county sheriff and the police chief in Kalispell, the F.B.I. took charge of the conspiracy investigation into possible links that Mr. Burgert may have had with other right- wing groups. The A.T.F. took charge of tracking all the weapons.

After a tip early last month from a Project 7 defector, the sheriff's department found two trailers packed with 30,000 rounds of ammunition, a broad array of small arms, body armor, pipe bombs, exploding booby traps, bomb-making chemicals and a vast inventory of survivalist gear and military rations.

"I think it would have taken hundreds of thousands of dollars to buy all that stuff at once," Detective Parish said. "So it is very possible that it was built up over several years."

What Project 7 was gearing up for, said the defector who tipped off the sheriff, was a round of assassinations in early summer. The sheriff's department discovered a list of what appeared to be targets that included local judges, the county prosecutor, the Kalispell chief of police, members of a police swat team and the dogcatcher.

Some of the targets worked at a police station in the nearby town of Whitefish, where Mrs. Brockway was employed. The sheriff said she had apparently sifted through trash baskets, gleaning information about where some officers filled their prescriptions and how others struggled with their weight. The sheriff's department found information sheets detailing her discoveries.

"The logic of their plan, if you can call it logic, was that by killing local law enforcement people, the state of Montana would have no choice but to send in the National Guard," Sheriff Dupont said. "Then they hoped to wipe out the National Guard. And then they hoped that NATO troops would be sent in and that would trigger an all-out revolution."

The sheriff and Detective Parish rolled their eyes incredulously as they explained what Project 7 hoped to accomplish. They suggested that Mr. Burgert was a blowhard who had bitten off more than he could chew. Investigators from the sheriff's department say they have identified four or perhaps five local people who were involved in the plot. Two of them, Mr. Burgert and Mrs. Brockway, are in custody. Two of the others have told investigators that while they knew about Project 7, they had no intention of killing anyone.

Sheriff Dupont learned of the plot in early February, after Mr. Burgert disappeared for nearly a month. Mr. Burgert's wife reported him mysteriously absent on Jan. 9. His pickup truck was found near a local river, with his fishing pole. His wife hinted to the sheriff's department that maybe he had drowned.

The sheriff's department, though, smelled a rat. Mr. Burgert had no hook on his fishing line and his tackle box, deputies said, was filled with lures that no respectable Montana fisherman would ever use.

On Feb. 7, Mr. Burgert, who had become a fugitive after failing to show up for a hearing on charges that he punched a sheriff's deputy in early 2001, was spotted coming out of Mrs. Brockway's home.

Her husband, Alan Brockway, also a suspect in the militia plot, left Montana for Israel several months ago. "The information we have is that he left because of the affair between his wife and Mr. Burgert," Detective Parish said.

After Mr. Burgert was spotted, sheriff's deputies staked out the house. When he and Mrs. Brockway drove off in a heavy snowstorm, deputies gave chase. Mr. Burgert slid off the road, but fled into the woods, carrying a rifle. After trackers found him and after an all-night standoff, during which Mr. Burgert held the gun under is chin and threatened to shoot himself, he surrendered.

All this happened in early February, which was when local investigators first got wind of Project 7 and the assassination plot. The sheriff's office kept the lid on its investigation, as computer experts from the state police tried Ñ and, so far, failed Ñ to crack encrypted information found on Mr. Burgert's home computer.

The lid came off on Tuesday, when Mrs. Brockway went to court for a bond hearing. On the witness stand, she announced the existence of Project 7 and local reporters began asking questions. Sheriff Dupont and other local law enforcement officials quickly decided to reveal the inquiry.

"The real scary part of this whole deal is, what if we had not got onto Mr. Burgert?" the sheriff asked in an interview on Friday evening in his office. "Could he have recruited enough people to execute the plan?"

Answering his own question, the sheriff said he doubted Mr. Burgert's conspiratorial skills. "It was always his mouth that got him in trouble," the sheriff said.