I've been starstruck since I was a kid growing up in Duluth, Minn., and watched Roy Rogers on the big screen. Every Saturday, come rain or shine, I was in the movie theater to escape what I figured was a pretty dreary life in what even then was becoming a rust-belt town.

So last August, as I checked in at the Century City Plaza, a luxury hotel next door to the old Century Pictures back lot, I kept pinching myself. I'd finally made it! I was in Tinsel Town. Not as a tourist, but as a bona fide member of a movie production company.

Wow.

The movie was Terminator 3: Rise of the Machines, starring Arnold Schwarzenegger, who was getting to a good age to become governor, but a little long of tooth, or droopy of butt (more about that later) to be a macho robot from the future brought back in time to help save mankind from evil machines. The production company wanted an author (they kept calling me a "real writer") to do the novelization of the movie. (Hollywood movies are often turned into novels that are released at the same time as the film, on the theory that fans who love the movie will buy the book.) They wanted someone with a strong science background who also wrote thriller novels. So they went to Tor/Forge Books, which is among the largest publishers of sci-fi in the country and which publishes some pretty decent thriller writers-including me.

My 69th novel, Joshua's Hammer, had hit No. 2 on Amazon's best-seller list, and I majored in math and physics in college, so my publisher called one afternoon and announced something to the effect that "Hollywood wanted Hagberg."

I was landed, hook, line and sinker.

Upstairs in my luxury suite, looking out toward fabulous Beverly Hills, I tried to strike an authorial pose, whatever that's supposed to look like, because someone from the production company would be coming over to pick me up for a conference. I'd been talking to the movie people by phone and e-mail for the past few weeks since I'd agreed to the deal, and I noticed they kept calling me the "real writer."

"We're really looking forward to having your input," the pleasant-sounding young woman who was handling what are called the sub-licensing deals told me. "Everyone is totally blown away, I mean excited, that we'll finally get to work with a real writer. It's totally cool."

My wife, Laurie, who can be brutally honest when it comes to my ego, reminded me on more than one occasion through all of this that although I am a writer, a damned fine writer in her estimation, for the purposes of this movie deal I was nothing more than one of the sub-licensees. That's on about the same level as the T3 video games or Schwarzenegger action figures that are released along with the film.

"Remember the Hollywood story Tony told you, about the dumb blonde who slept with the writer in the hopes of getting the part?" Laurie prompted. Writers, Tony had warned me, were at the very bottom of the Hollywood pecking order.

Tony Ray, who was executive producer on the Bette Midler movie The Rose and also on Harry and Tonto, had a lot of pithy things to say about Hollywood. He'd run away from the place with his tail between his legs, damned near wrecked mentally as well as physically.

I got to know him briefly a few years ago when we were across-the-street neighbors and he found out that I was a novelist. Over a couple of beers one afternoon we talked about his background and what Hollywood did to people in general, and specifically what it did to "real writers."

"Look what it's done," he said in his voice that sounded like gravel from years of smoking and drinking and lots of other things. "It killed Fitzgerald, ruined Mario Puzo, who ended up writing garbage, like screenplays for disaster flicks. Heck, even Hemingway admitted defeat."

"Yeah, but those were the old days," I argued. Anyway, Tony was a self-admitted basket case. What did he know? "We're more sophisticated now," I said lamely.

"Listen real close. You get a Hollywood contract, stay out of California. At all costs. If they send you a contract, drive to the California-Nevada border-make sure that you stay on the Nevada side-hand over the signed contract and have them toss over the money. Then get in your car and drive away as fast as you can."

Standing at the floor-to-ceiling windows looking out toward Beverly Hills, I wasn't thinking about Tony's dire warnings. I was in Hollywood. I was going to meet the producers and director of a movie that had already cost them $180 million and change. A major business venture they hoped would earn them, worldwide, a nifty $1 billion.

I was going to a cutting room at Sony Pictures, and sometime over the next day or two Laurie and I were going to be wined and dined-at Spago, as it turned out-and we would be treated to a VIP tour of Warner Brothers studios. T3 was a joint Sony-Warner Brothers production, because, it was explained to me, nobody has a couple hundred million to put on the line without some help.

Let me clear up a couple of points for the Hollywood uninitiated, which as a nouveau but earnest insider I'm happy to do. The movies Terminator and Terminator 2, both directed by James Cameron, were huge box-office successes. But then the whole Terminator thing sort of languished for want of anybody's enthusiasm. Cameron was apparently done with the idea, as was Linda Hamilton, who had played the angst-ridden mother of John Connor, the savior of mankind in the future.

But a production company was formed, the rights for the Terminator character were purchased for a few bajillion dollars, and a concept for T3 was created which would give Schwarzenegger more lines than in the previous two flicks.

After all, the Terminator movies might be able to survive Cameron's absence, and even Linda Hamilton's lack of on-screen presence; but Terminator equals Schwarzenegger. It was a no-brainer.

With the rights in hand and the concept for the story in mind, they approached Schwarzenegger with a check for $30 million. Another no-brainer.

But then the fun started.

The young but very talented director Jonathan Mostow, hired for $1.5 million, had only done one real picture of note, which was the World War II submarine thriller U-571, starring Matthew McConaughey. Mostow's concept for T3 was to make a terrific nonstop-action flick with a gangbusters super-surprise ending.

But in Mostow's mind, a surprise meant that only a handful of people could know what the true ending was going to be. Which, considering that it takes 2,000 people to make a movie, is a stretch. But Mostow was serious. The ending was going to be a national secret, as secure as anything the CIA was zealously guarding. Woe betide the hapless fool who even hinted at violating this sanctity.

In practical terms, this meant that the script I was given from which I was to write the novel was missing the crucial last five pages.

"No problem," I was told. "Write anything you want to write, and when you deliver the book we'll take care of it. You'll do just fine," they said. "After all you're a real writer."

OK, it wasn't such a big deal after all. I mean, after 120 pages of screenplay, the movie couldn't go in too many different directions in the last five pages. Connor and Kate Brewster, the character who would be his wife in the future, were sealed in some sort of a tunnel beneath a very remote military base in the mountains far to the east of Los Angeles; the world was about to come to an end; the Terminator and Terminatrix were both destroyed. So how much more could happen?

I wrote my version of the ending and turned it in. That's when the trouble started.

The director's first reaction was to cancel the entire book project-err, sub-license. "Just forget the entire thing." I was told that Mostow might be worried that my ending was better than the ending he'd filmed, and he'd be darned if he was going to be shown up by some thriller writer, even if he were a "real writer."

But the money guys wouldn't hear about that. Mostow was the director; but like me, he was only another hired gun on the project. There was a bigger picture to consider, one of making money, including on a book version of the film.

A couple of days later a FedEx envelope showed up on my doorstep with the last five pages of the screenplay, revealing an ending that wasn't so terribly different from mine. So I rewrote the thing to comply with the movie version, and that was the end of that.

Or so I hoped.

I should have known better, because I'd already labored over some other nagging problems that, I would remember later, Tony Ray had warned me about.

Magic occurs when larger-than-life actors appear on huge screens, complete with scintillating action, dazzling special effects and fabulous music. Movies can make just about anything seem real, any situation perfectly logical. But in the slower-paced, more cerebral world of the novel, it ain't so easy.

Just one example in the T3 project: The Terminatrix (T-X, for short) is constructed of titanium, carbon nanofibers and other exotic, futuristic materials. In one scene near the end of the movie, T-X is chasing John Connor and Kate Brewster through the tunnel of a really big particle accelerator when its super-huge electromagnets power up. T-X is pulled off her (its) feet and slammed up against the tunnel wall, where she is held fast.

Works great in the movie.

But not in a novel.

Titanium, carbon nanofibers and other exotic future materials are nonmagnetic. That problem suddenly occurred to me in the middle of the night when I woke in a cold sweat. Moviegoers would gloss over the trouble, but my readers wouldn't.

After a couple hours of brainstorming, I came up with a solution. T-X was a robot, with mechanical joints that needed lubrication. So why not make her lubrication something futuristic like artificial liquid steel-something for which an electromagnet could feel a real attraction?

There's another thing I want to clear up about the movie business. Combine all book publishing, novels, cookbooks, how-tos, comics, the whole enchilada, and you come up with a $25 billion industry. T3 all by itself hoped to gross $1 billion. Just one movie!

The movie industry trumps the book industry. It's a simple matter of economics. What this meant as far as my deal went is that I almost went to jail.

Jonathan Mostow, the director, wanted the ending to remain top secret. He was forced to share that ending with me so I could complete the novel. But he didn't want anybody else to see it.

That meant he didn't want my editor or my publisher to know how the story ended. I guess he, too, figured that I was a "real writer," so I wouldn't need any editing, and my publisher wouldn't have to see the manuscript. Heck, the book could publish and distribute itself!

Of course the other 2,000 people who worked on the project knew the ending. Even the guards on the back gate at Sony Studios knew the ending! The day I was there to meet with Mostow about the project, since I had to wait at the gate for an escort to come get me, I chatted with the guards.

"You're here for T3," one of them said.

"Yup. I'm doing the novel."

"Great ending," the other guard said. "You'd never guess the underground place was a bomb shelter."

The first guard shrugged. "You'd never guess that they hired a real writer," he said.

I offered my novel manuscript on eBay for trivia collectors, for delivery after the movie debut, with no hint of the ending.

Within 24 hours an FBI special agent from the Los Angeles office telephoned me with dire warnings about national security-no kidding-for even hinting that I would reveal the ending of this movie before its release date, which was about three weeks away.

Being the nonconfrontational guy that I am, I mentioned, but did not really emphasize, something to the effect that with all the Osama bin Ladens of the world running around threatening the security of the nation, didn't an FBI agent have something better to do than be a flack for some comic book movie?

That did not go over well, and our telephone conversation ended on a less than friendly note.

But, standing at the window in my luxury suite, looking toward Beverly Hills, all those wrinkles were in the future. As were the realizations that my publisher would probably lose a lot of money on the deal, and I would make little or nothing for my work because of something called creative accounting. But then, that's show biz.

At that point I was blissfully unaware of a whole bunch of other things as well, just as I had blithely forgotten all of Tony Ray's warnings about watching my back in Hollywood.

Tony had told me that the key to success in Hollywood is sincerity: "If you can fake that, you've got it made."

Early in the movie Arnold Schwarzenegger, as the Terminator, shows up in the present time in the buff. It's the way the time-transport machine works.

He walks across the desert and enters a roadhouse, where he takes the leather trousers and jacket from an entertainer. As he walks across that desert, the moviegoers get to see the naked Arnold from the back.

Great butt, you might say. Especially for a guy his age. How many other governors have butts that nice?

It wasn't his butt.

In the stills I saw, Arnold is wearing blue tights.

It means he had a butt double.

"Hey, real writer," my wife called from the door. "Time to go. Your adoring public is waiting."

I dragged myself away from the floor-to-ceiling window, in which I could see my really quite photogenic reflection. So Hollywood was a little flaky around the edges. What the heck? It was show biz.

I'd be back.

I guess.

At least as close as the Nevada-California border.

David Hagberg is a former Air Force cryptographer who has spoken at CIA functions. He has published more than 20 novels of suspense, including the best-selling High Flight, Assassin and Joshua's Hammer. He currently lives in Sarasota.