The group called itself "The Family." After meticulously casing a horsemeat packing plant in Redmond, Ore., they made a firebomb using soap and petroleum products (a napalm-like substance known as "vegan Jell-O") and a time-delayed incendiary device called a "Cat's Cradle."

Arriving at the staging area after dark, they dressed in dark clothing, masks, and gloves, and checked their walkie-talkies and police radio scanner. Quietly, they crept through the sagebrush toward the target. They drilled holes through the wall so the fuel would pour into the building. Then, they set the firebomb against the wall and retreated to the staging area. There, they dumped their dark clothes and shoes into a hole and poured in acid to destroy DNA and other evidence. By the time the packing plant, Cavel West, Inc., was engulfed in flames, "The Family" had vanished into the night.

Five days later, through an anonymous communiqué, the Animal Liberation Front (ALF) took credit for the fire that destroyed the facility in July of 1997. But it would be years before the alleged plotters were apprehended. And until then, according to a 65-count indictment announced last week by the US Justice Department, the 11-member group of activists launched 17 similar attacks across Oregon, Wyoming, Washington, and California in what authorities consider one of the most extensive campaigns of "ecoterrorism" in US history.

Documents and other information revealed in recent court hearings provide an inside look at how a band of extremists - 20th century Luddites, in a way - tried to leave their explosive imprint on a society whose commerce and industry they believed was overwhelming nature.

Edward Abbey, the desert curmudgeon whose 1975 novel "The Monkey Wrench Gang" inspired the environmental group Earth First!, once declared that "sentiment without action is the ruin of the soul." Most who took this to heart had no intention of breaking the law.

But somewhere along the way, vandalizing log trucks and "liberating" lab rats escalated into firebombs, plots to blow up electrical towers and dams, code names, and anonymous communiqués boasting of destroying millions of dollars in property.

Other targets allegedly attacked by "The Family," for instance, include US Forest Service ranger stations, wild horse corrals used by the US Bureau of Land Management, a Bonneville Power Administration electrical tower, and an SUV dealership. There were also three forest products companies, the University of Washington Horticultural Center, a Colorado ski resort, and a police station in Eugene, Ore.

While the attacks occurred around the West, 12 of the 17 were in Oregon, most within an hour or so of Eugene. Like Berkeley, Calif., Madison, Wisc., and Boulder, Colo., Eugene is a university town known for its liberal politics. But it's also home to more radical thinking as well, including anarchists behind much of the rioting and destruction at the 1999 World Trade Organization meeting in Seattle.

Those close to the underground activists say the FBI has targeted the wrong people. "What law enforcement has done is round up a bunch of above-ground, well-known, peaceful animal-rights activists and environmental activists and charged them with being members of the ALF and the ELF [Earth Liberation Front] simply because they can't find the real members," says Jerry Vlasak, spokesman for the North American Animal Liberation Press Office in Canoga Park, Calif. "These people are completely innocent of the charges."

Many of those charged appear to have led unremarkable lives in recent years. Suzanne Savoie works in a home for the developmentally disabled here in Ashland, Ore. Jonathon Paul, who lives with his wife in the mountains nearby, trains people who fight wildfires. Kevin Tubbs has been an assistant manager at a department store. Chelsea Gerlach is a disc jockey in Portland whose father works in the timber industry.

Yet modest, unassuming lives may have masked ideals and activism that went beyond the mainstream. Thirteen years ago, Mr. Paul spent six months in jail for refusing to testify about convicted ALF arsonist Rod Coronado. Mr. Tubbs once worked for People for the Ethical Treatment of Animals (PETA). As a sophomore at South Eugene High School, Ms. Gerlach wrote in the school yearbook: "Our generation was born to save the Earth - if we wait until we're out of school it might be too late."

Among activists, the recent arrests have brought a sense of fear and loathing - fear that there may be more to come from the police agencies that seem to have cracked the super-secrecy of ALF and ELF, and loathing for the informants who apparently enabled the breakthrough.

Activists writing online blogs have issued veiled threats against two "snitches," one of whom has been charged in the destruction of an electrical transmission tower in 1999. The sister of one of the informants, describing herself as "brokenhearted," speculated that law-enforcement officers may have provided drugs to her heroin-addicted brother.

"Just assume every conversation you have is bugged, assume everyone is an informer if you must, and don't talk about ANYTHING to ANYONE," another person wrote on an Internet site.

That warning seems to be well-founded. Evidence supporting the indictments reportedly includes 35 compact discs of recorded conversations and 40,000 pages of transcripts, police reports, and photos. Earlier this month, three more people were arrested for conspiring to destroy a US Forest Service genetics institute near Placerville, Calif.

In his affidavit to US Magistrate Gregory Hollows, FBI Special Agent Nasson Walker revealed that the investigation involved "a confidential source who is deeply embedded with the subjects' cell." The paid informant secretly recorded conversations, sent text messages from her cell phone about ELF activities, and occasionally had clandestine meetings with FBI agents.

The recent arrests mark a breakthrough for the FBI in its fight against what it calls "ecoterrorism." But the story is far from over. Some 1,200 such incidents have been recorded in recent years from Oregon to New York. ALF/ELF and their defenders point out that no fatalities have resulted. But property damage has totaled more than $200 million.

Both sides in the struggle understand its seriousness. "Persons who conduct this type of activity are going to spend a long time in jail and they should understand that, regardless of the motive," FBI Director Robert Mueller said.

Mr. Tubbs, now awaiting trial, no doubt has that possibility on his mind. Supporters have set up a "book wish list" for Tubbs. Among the volumes he'd like to read: "Prison Etiquette: The Convict's Compendium of Useful Information."