John Orr was an acclaimed arson investigator, and when he wrote a novel he drew upon his expertise: His villain was a firefighter-turned-firestarter.

``He felt fright but it excited him. ... His fires gave him the much-needed attention he craved, providing him with feelings of importance and recognition,'' Orr wrote in his unpublished book ``Points of Origin.''

``He was, after all, the only one person who knew how the fire started. And didn't that make him a very important person?''

If that passage seems eerie _ if it seems that Orr had a window into the arsonist's soul _ there is good reason.

Orr set fires.

A fire captain in Glendale, Calif., Orr was arrested and convicted of setting three fires in 1992 while driving home from an arson investigators' conference in Fresno _ just like his fictional character.

After he was sentenced to 30 years in prison, Orr confessed to setting three more fires. And he is charged with a string of others, including one that killed four people (including a toddler) and another that destroyed 67 homes.

``There was shock, outrage, feelings of betrayal, just as there would be in any profession when one of your own does something heinous and catastrophic,'' said David Hillman, president of the California Conference of Arson Investigators.

``But hey, it's going to happen any time you have this many people involved in a profession and there's such a fine line between the good guy and the bad guy. Sometimes a person can drift over the line.''

How often does a firefighter cross the line? No one knows. But headline-grabbing clusters of firefighter arsons have led states from Delaware to California to deal with the problem.

``Peopled in the fire service are concerned. They're kind of the last of the good guys, and every case tarnishes their name,'' said Marcel Chappuis, a clinical psychologist and consultant to the Utah Fire Marshal's office.

``Fire service is paradoxical _ long hours of nothing and short bursts of intense adrenalin rush,'' Chappuis said. ``These guys are waiting for the bell to go off. They want to be busy, to perform, to be involved. They want to be the hero. A lot of times these guys make work for themselves.''

Says Peter Sparber, a consultant to the National Volunteer Fire Council: ``We think it's relatively rare. But it's an underlying truth that those who are fascinated with fire sometimes join the fire service. You're going to have a couple of oddballs every so often attracted for the wrong reason.''

Generally, arson is associated with insurance scams or revenge. But the motives are different for public servants who become public menaces, even though some volunteers get a stipend of $5 to $10 for each alarm answered.

Some crave excitement because they went through rigorous training and found the job more tedious than expected. Some want to prove themselves to their peers. Some relish the pats on the back for putting out a fire.

They usually start with grasslands or woods, then escalate to trash bins, abandoned cars, storage sheds and unoccupied buildings, according to Timothy Huff, who did a study of 75 firefighter-arsonists using a model at the FBI's National Center for the Analysis of Violent Crime.

He noted one case in which a volunteer set fire to his fire station.

The best prevention, according to Huff and others, is to screen applicants with background checks.

Utah has a computerized network that any fire company _ either volunteer or career _ can tap into to see if any applicant has had a history of firesetting.

Action was taken partly because seven firemen in the Milford area were found to have set 23 fires several years ago, according to state Fire Marshal Lynn Borg. One of the firefighters even tried to throw off investigators by burning down his parents' garage.

``In a lot of little rural towns, there's not much excitement going on. A lot of them like to drive the fire truck and turn on the sirens and flashing lights. They really get wound up over it,'' Borg said.

But volunteer companies _ whose ranks make up 75 percent of all U.S. firefighters, according to the National Fire Protection Association _ often lack the resources to do background checks.

``I believe (firefighter-arson) happens much more frequently in volunteer departments,'' said Kenneth Fineman, a forensic and clinical psychologist at the University of California who has studied the problem.

``In the average volunteer fire department, it's catch as catch can. They're glad to get somebody, anybody'' Fineman said.

Delaware started lecturing recruits in 1993 about the consequences of fire setting _ prison time, humiliation, scorn and contempt _ after 14 volunteer firefighters were arrested within a two-year period. All but one of the state's 61 fire companies are volunteer.

New York adapted Delaware's three-hour course after 35 firefighters were arrested for setting fires in 1993, including 10 in Suffolk County on Long Island within 12 months.

Now, the first lecture of the first class on the first day of instruction at the Suffolk County fire academy deals with arson. Officials also produced a five-minute video entitled ``Firefighter Turned Arsonist.''

``Anyone come here to set fires? Put your hand up so I can get your name now,'' said Chuck Dohrenwend, commander of the Suffolk County arson squad, addressing a group of 20 recruits.

Then holding up newspaper headlines, he said, ``This is what happens when you guys screw up.''

Louis Gelsomino, 19, of Sayville, is serving 15 years to life in prison on two counts of second-degree murder. He confessed to burning what he thought was a vacant building, but two people who lived inside perished. Gelsomino, whose uncle is a fire commissioner, had been a junior firefighter for three years.

And Lt. Kevin Heffernan, 23, of the Smithtown Volunteer Fire Department, is serving 18 months to four years in prison after pleading guilty last year to setting three fires in abandoned buildings.

In each case, Heffernan helped put out the fires; he told a judge he wanted to impress others by being first to answer the alarms. Two firemen _ including the brother of one of those arrested _ were injured battling the fires their colleagues had started.

``Has a cop ever sold drugs? Yes,'' said David Fischler, Suffolk County fire marshal. ``Has a teacher ever molested a kid? Yes. Even priests aren't exempt. Every profession has its bad apples. We're going to do everything we can to get rid of them in ours. If you set one fire, you stop being a firefighter and you become a criminal.''

Fire companies afflicted with a firebug say it can take years to rebuild public trust. In Smithtown, N.Y., firefighters helped raise money to pay off fire damages caused by their own members.

``Most guys can't comprehend the idea of setting a fire for the thrill of putting it out. They've dedicated their lives to the exact opposite,'' Fire Chief Bob Chester said.

South Carolina is working to implement a training program after 47 firefighters were arrested on arson-related charges in 1994 alone.

Last May, state fire service officials asked that an alert bulletin be posted in every fire station listing this profile of a firefighter-arsonist:

_A volunteer, white, male, age 18-25.

_Highly trained, motivated, ``firefighter of the year'' type.

_Always seems to be in the right place at the right time.

_Works in low-paying jobs with low recognition and esteem; therefore joins the fire department for recognition.

_Other characteristics may include unstable home environment as a child; poor relationship with father; poor to average academic record; ineffective relationships with women; personal stress; alcohol use.

``Any state that says they don't have a problem has their heads in the sand,'' said Bill Graham of the South Carolina Law Enforcement Division. ``We're policing the very people who are supposed to be protecting the public from fires. It has gotten progressively worse.''