People in Lincoln, Mont., thought of him as the ultimate recluse -- in a town that was already isolated, he chose to live five miles away in the hills. So far had Theodore John Kaczynski removed himself from society that an FBI agent watching his cabin from a snowbank once saw a cougar stalk and kill a deer.

Kaczynski lived by himself without a telephone, electricity or running water. With no sewage hookup, he used his feces to fertilize his vegetable garden, residents said. Wearing soiled, threadbare overalls or jeans and a straw hat, the bearded loner would ride his bicycle down into town for supplies or long visits to the public library. When the snow was deep, he'd hitch a ride on the mail truck, or walk.

Like Kaczynski himself, the cabin seemed rough and wild on the outside; garbage cans overflowed with refuse and beer cans were strewn about the yard. But the jumbled exterior gave no hint of what lay inside. The 10-foot-by-12-foot cabin was "wall-to-wall books," according to a neighbor, the only indication that the reclusive mountain man had another life as a Harvard-trained mathematician, who according to the FBI became one of the nation's most wanted terrorists.

"They were not thrown about but neatly stacked along the walls," said Lee Mason, who lives less than a mile away. "The only other thing I saw was a table and a chair." Mandy Wilson, who delivered his firewood, recalled seeing a large number of candles, apparently to read by. But outside the cabin, "It looked like a few things had been let go," Wilson said.

Few locals knew his name. "He was a real shy man," said Theresa Brown, 21, who works at a Lincoln store, Garland Town and Country of the thin-lipped, five-and-a-half-foot tall hermit, who wore his graying blond hair at shoulder length.

Kaczynski had lived in the town for more than a decade, but no one interviewed yesterday knew about his Harvard degree or his talent for mathematics -- or, if the FBI is correct, his affinity for building bombs.

Kaczynski was born May 22, 1942, in Chicago, and grew up in the working-class suburb of Evergreen Park. He entered Harvard in 1958 on a scholarship; the freshman class register said he was to study mathematics and physics.

While at Harvard, Kaczynski lived in Eliot House, known at the school as a preppy haven. But he didn't make much of an impression there with housemates. "As soon as I saw his face I certainly recognized him," said Harvard law professor Laurence H. Tribe a housemate who also studied mathematics. "I must have seen quite a bit of him, but at the moment I don't remember anything about him." Another had "the vaguest recollection" of him, adding that Kaczynski was "not a joiner." Yet another, conservative activist Howard Phillips, said that he did not remember Kaczynski at all: "Sorry I don't know anything -- but I'm probably safer because of it."

After completing his degree at Harvard, Kaczynski went on to the University of Michigan, where he completed a dissertation on mathematical "boundary functions" in 1967 and produced a body of a half-dozen scholarly publications. He moved to Berkeley in 1967 and taught in the mathematics department between 1967 and 1969 as an assistant professor. Again, he did not seem to leave much of an impression in Berkeley before resigning in 1969.

It was at that point that the world seemed to lose sight of Kaczynski; he last published a mathematics paper in 1970. Then after a nearly a decade, the world began to hear from the terrorist that the FBI dubbed "UNABOM." The bomber chose targets in the universities, airlines and in the computer trade. The first attacks occurred at Northwestern University outside of Chicago in 1978. Kaczynski lived for a time in Salt Lake City, according to news reports; the single UNABOM sighting occurred in that city in 1987. In all, the bomber has committed 16 attacks, killing three people and injuring 23.

Harvard keeps very good track of its graduates, but lost sight of Kaczynski over the years. He gave legitimate addresses for the class directory until 1977, listing residences in Iowa one year; Great Falls, Mont., another. But the 25th anniversary directory for his class lists his last known address as 788 Banchat Tesh, Khadar Khel, Afghanistan, a place that does not appear in standard geographic indexes. The 30th anniversary directory, published in 1992, gave the same entry, as his "last known address."

By then he had made his way to Lincoln, though it is unclear when he arrived there. One resident recalled that Kaczynski was already living outside of town in the 1970s. Lincoln is a small town in a sheep and cattle ranching area of Montana, situated on the Blackfoot River -- made famous in the movie "A River Runs Through It." The town has gained additional notoriety because of plans to build a large mine where gold would be leached out of crushed rock with a cyanide solution. Local environmentalists fought the proposal, fearing that the project would damage the pristine river.

Residents of Lincoln said Kaczynski didn't hold a job, and many of them assumed that he was living on family money because he never ran up debts and seemed to have ready cash for necessities like firewood. He was living frugally: Cindy Davis, who used to run a second-hand store in town, said Kaczynski would occasionally load up on free clothing donated to her store by other residents. And two years ago a neighbor gave him a bicycle to replace one that had worn out. Still, Davis said, he bought "a lot" of history books.

Six weeks ago he applied for a job at a local general store, Blackfoot Market. The store wasn't hiring. "I didn't need the extra hand," said Jay Potter, the owner.

He might not have been cut out for the retail trade, however, because Kaczynski wasn't much of a talker. "He'd just get to the point and be done," said Brown. "He never got into much detail about anything. Like, he wouldn't talk about the weather and stuff."

"You would say `hi,' and you would be lucky to get a `hi' back," said Rhoda Burke, a cashier at D&D Food Town. "We didn't appreciate him coming in because he generally had such bad body odor. It was as if he never bathed."

Blackfoot Market co-owner Karen Potter said that Kaczynski would come into her store to buy canned meats and stone-ground flour to bake his own bread at home. She added that he struck her as very intelligent, "mainly in the way he rebuffed questions," she recalled.

"When the authorities told me they were looking for a Harvard graduate, he was the first person who came to mind."

Staff writers Curt Suplee in Washington and Tom Kenworthy in Denver contributed to this report.