(FORTUNE Magazine) – It was just a couple of months ago but a lifetime away, as far as I'm concerned, because the episode has changed my whole worldview. Like, there was Before Lenny and now there's After Lenny, and nothing will ever be the same, except, probably, for Lenny. People like Lenny don't change. They just reveal themselves over time. And if they don't do so until it's too late? Well, so much the worse for you.

Lenny was a friend of mine. Not a bosom buddy but, you know, one of the ten or so guys you hang around with when you get settled in a city. He and I were in the same business--you don't need to know what business, it's none of your business--but we played cards and drank and, I believed, felt affection for each other.

One day in early spring I got a call from my man Lenny. "Bing," he says, "I'm working with the Barfinger people on a Best Practices study, and I wanted to look at you guys as an example of what's possible in this business."

In other words, Lenny was working with a consultancy that studies good companies and then sells insights to others that are feeling clueless. It was Lenny's goal to study the way we do things, holding it up as a beacon to others. I was flattered.

"We don't usually participate in this kind of thing," I told Lenny.

"Don't worry," says Lenny. "I admire you guys. I worship Carver and think he's just about the greatest who ever did what he does." Carver is the venerable leader of this part of our operation.

"Listen, Lenny," I said, remembering how many of the consultants I have worked with have been total pricks. "I'm gonna let you in to do this thing because I think you're right. I think we're pretty great, and we could make a really good case study. But I'm gonna vouch for you here, and if you screw me, I'll be bacon."

"Bing," says Lenny, sounding somewhat hurt. "We've known each other 20 years."

So I let him in. Call me a fool. Go ahead, I'm begging you! You can't possibly be as contemptuous of me as I am of myself.

Lenny went about his work. He sat in on things. He talked with people. And phone calls started coming in to me. "You vouch for this guy?" they'd ask. And I'd say, Yeah, don't worry, he's a friend.

And he was, too. He was.

A week before the case study was supposed to be done, I got a call from Lenny. "Gee, things are going so well," he said. "And there's this goodbye party for Carver I would really love to be at. It would be a great kicker to my report."

"Lenny, man," said I, "there will be very, very few outsiders at that thing." But he pleaded, and I thought, Hey, we're in this deep--why not give the guy what he needs? Lenny was at the party. He appeared kind of furtive, and he didn't look me in the eye.

A couple of days later I got a call from Carver. It was hard for me to understand him because he was screaming at me. It seemed my trusted pal had been asking around about certain aspects of the old man's private life, raising questions that were not what I would call ... congenial. That distressed me. I remembered all the things my friend had said to me while he was imploring me to help him pursue his lucrative piece of consulting business: How he idolized Carver. How he wanted to "celebrate" our operations. How he would never do anything to harm my reputation with the guys in the field.

I called Lenny. I was kind of angry. He was quite the cool customer.

"You have to understand the nature of the consulting business," he said to me.

"You have to understand the nature of friendship," I replied.

"There are a couple of people you could talk to at the Wharton School of Business who could explain the process of this kind of case study to you," he said.

"Up yours, Lenny," I said. It was probably not the most cogent reply to his kind suggestion, but it was the best I could do because the amount of blood in my eyes was making it difficult to see. I hung up. We haven't spoken since.

The case study came out the following week. It was vicious, unforgiving, mean, and shallow, functioning to make the consultant look smart and savvy and his subjects the opposite. It was all he had said it wouldn't be. My friends in the company were hurt. Carver is no longer my friend. And it was my fault. Because I was a credulous dummy who believed in the myth of friendship.

I now I find myself unable to swallow the whole situation. It's like a stone caught in my throat, and I just can't force it down. I dream of strangling Lenny. Every now and then he pops up on some marginal cable channel, talking about us quite expertly, and always to our detriment. I feel as if something crucial to me has been lost. And maybe it has ... maybe it has ...

What is the value of our illusions? What is life worth without them?

Stanley Bing is an executive at a FORTUNE 500 company he'd rather not name. His most recent books are The Big Bing, a collection of essays, and You Look Nice Today, a novel. He can be reached at stanleybing@aol.com.