(FORTUNE Magazine) – FORTUNE's Ronald Henkoff met with Mark Whitacre in North Carolina and New York. The following interview focuses on the reasons behind his falling out with the FBI--beginning with his original contact with special agent Brian Shepard. Excerpts:

When you started working with the FBI in November 1992, you and Brian Shepard got along fine, didn't you?

Sure. That first evening we talked he was real easygoing. We talked about price-fixing meetings until two in the morning. ADM wasn't fixing prices yet, but we were heading there. He was taking notes like crazy. He would say things like "Wow!" and "You're kidding me." You could tell he felt like he had hit a gold mine.

And within days you began taping your colleagues at ADM. How did that feel?

Nerve-racking. The FBI gave me a little microcassette recorder that you could put in your jacket pocket, but it had a wire with a mike on it. I had nightmares that people would see the mike.

Was there a rush from doing this--you know, that you were doing something secret?

No. I never felt like a secret agent man. But I did feel pumped. I felt that I was doing a good thing. Brian told me that I was going to be doing the country a great service, that I was taking heroic action.

The thing that kept me going was that I was sure I was doing the right thing. I was not getting depressed at all yet.

In December 1992, the Justice Department asked you to sign a cooperation agreement. Did you show it to a lawyer?

No.

Why not?

I read through it, and I said, "Brian, there are a lot of things I don't understand. I think I should show it to an attorney." And he said, "Mark, I'm telling you, if you show an attorney this, you'll jeopardize the whole case. ADM has tentacles everywhere. They know all the attorneys you know, in Decatur, in St. Louis, anywhere in the Midwest, even in Washington. We're telling you right now that you can't see a lawyer."

So you signed the agreement?

Yes. The impression I got from Brian was that we could work together with or without an agreement. But I must say that this was one of the first things that I felt a little uncomfortable with, because I didn't understand what I was signing. Looking back, I should have never signed that agreement.

Why not?

Because it was so one-sided. It was all about protecting their interests, not mine.

Did the FBI ever warn you that you might be a suspect in the price-fixing investigation yourself? Did they ever read you your Miranda rights?

Never.

Once you became an informant, did your travel get in the way of the investigation?

Yes. Early on, about February 1993, the Japanese were wanting to set up the next meeting on price fixing. But the scheduling problem was me, and Brian knew that. One night we were in a room at the Holiday Inn in Decatur, and Brian heard the tapes saying that the Japanese wanted to meet. And he knew I was holding up the dates for another price-fixing meeting, and he was really pissed off.

What did he say?

He took a briefcase, a hard-sided briefcase, and he took it by the handle, swung it around and hit me on the right arm. He said, "You've got to make this investigation your No. 1 priority, Mark."

Did you tell anyone about the incident?

That night I went home and told my wife, showed her my arm. It was red. It was bruised by the next day. I went over to my in-laws' house and showed them too. And I told two of my friends about it. So I've got at least four witnesses who are willing to go on the stand and talk about this. I also called Dean Paisley at the FBI's office in Springfield, Illinois. And his only comment was, "Look, Brian's the agent that you're working with, and it's best if you take your issues up with him."

So you kept on working with Shepard?

Right. I was making tapes on a regular basis. Brian and I would meet a couple of nights a week in the parking lot of St. Mary's Hospital in Decatur. That was our key drop-off zone. Sometimes we'd meet for five minutes. I'd tell him what the tape was about, and he'd leave.

Things were going real well with the lysine investigation, the product in my division, the one I knew the most about. But Brian wanted tapes on high-fructose corn syrup and citric acid, even though those products weren't in my division. A big chunk of ADM's profits came from fructose. Brian was really enamored of that. The other thing he was really in awe of was Cargill, a major competitor in fructose, four or five times the size of ADM, one of the biggest private companies in the country. He said, "Mark, there's got to be a tie between ADM and Cargill on fructose. I want you to ask [ADM vice chairman] Mick Andreas and [corn-processing division president] Terrance Wilson as much as you can about fructose."

Did you manage to do that?

I tried. I went to Mick, taping all the time, and asked, "Hey, how are we doing in fructose? Surely with fructose prices doing so well, we must be doing the same kind of price fixing with Cargill that we're doing with the Japanese in lysine?"And Mick said, "Look, Mark. Cargill's not going to fix prices. I could call Ernie Micek [then a senior executive at Cargill, now the company's CEO] today, but he would hang up the phone if I tried to talk to him about what we could do to increase prices."

What did Shepard say when you played that tape?

This was March or April of 1993. And he said, "I'll tell you what, Mark. This case is in the early stage, and I'm not getting a lot of time for this case. This case is very important to me, and this tape is not good for us, not good for this case. Which means it's not good for you either, because you are a part of this case now. The best thing that you could do with this tape is to take it home and destroy it." He told me, "I can't take this tape. If I take it I'm in a lot of trouble, because we have rules and regulations. But you're an informant. You work at ADM, not at the FBI. You don't have rules and regulations about what tapes you give me and what tapes you don't. Take that thing home and destroy it."

Is that what the FBI had told you to do?

What they told me originally was that everything I taped I should give in.

So what did you do?

My wife, Ginger, and I made a decision that if I destroyed a tape, and later on somebody found out there was a tape that I destroyed, then they'd blame me, not the FBI. They could get me for obstruction of justice. So I made a decision not to destroy that tape. I labeled it, dated it, wrote down the topic--conversation with Mick about Cargill--and kept it.

What happened next?

Then, the next time I met with Brian, a couple of days later, I turned on my tape machine before I pulled into St. Mary's parking lot. So I'm in my car and Brian gets in. The first thing I tell him is, "Brian, by the way, I got rid of the tape. That tape we discussed, where Cargill would never fix the prices of fructose." And he said, "Good, good. I don't even want to know how you destroyed it. The main thing is that you got rid of it." That was the very first tape I made of Brian Shepard. All I was doing was protecting myself. Later on, if they said, "Mark withheld a tape," I'd say, "Not only did I not withhold it, here it is. And here's a tape of the guy who told me to do it."

Okay, so then you started building a collection of tapes.

Right, within a week or two, I also started making copies of the price-fixing tapes I was handing in.

And why did you decide to make copies?

Because I figured if there were certain tapes Brian was telling me to take back, what if there were also tapes I was giving him that he wasn't turning in himself? What happens if one day the whole case comes to a head and I remember something, but the government says, "We never heard any of that stuff. It's bullshit." Well, then I could pull out my copy.

How many people saw the tapes and knew what you were doing?

My wife, some of my relatives, a few good friends. Sometimes they would ask: "Hey, who are the good guys here?" It came to the point, after four or five months, where I wasn't sure who was dirtier, ADM or the FBI.

So how often did Shepard tell you to destroy tapes?

Four, five, or six times.

All right, so you're building up a tape library. What were you thinking?

I was getting very depressed. I was realizing the FBI was not much different than ADM. They all had their own conspiracies. And I was just stuck in the middle. For the first time in my life I was very, very depressed. My wife noticed it. My in-laws noticed it.

Did you tell the FBI you were depressed?

In the spring of 1993, I told Brian Shepard and another FBI agent that I was considering killing myself. And I've got this conversation on tape too. I'll never forget this. They asked me how I would kill myself if I did. And I told them I would do it with sodium cyanide. I'd take some and swallow it. This discussion about my depression went on for a couple of weeks.

Did you try to get some medical help?

Brian said, "Well, if you ever get depressed, you can call and talk to us anytime." And I said, "You know what, guys? I need more than that. I was an enthusiastic guy before November 1992. I really want to see a doctor, a psychiatrist."

Did you end up seeing a doctor that first time you got depressed?

No. The FBI told me: "You can't see a doctor. It would destroy the case. The same way if you saw a lawyer it will destroy the case. ADM will find out, and we'll find out."

You say they also kept saying you'd be a hero. What did you think about that?

I liked it. When you're in a manic state, you're very grandiose--you know, go to work every day thinking I could be the next president of the company, and not thinking about the fact that I was bringing down my bosses.

Which bosses were you bringing down?

Well, I had [ADM chairman] Dwayne Andreas on a couple of tapes as he was being updated on the price-fixing discussion. And [ADM president] Jim Randall was on tapes a lot talking about ADM stealing technology. I had Randall walking in on price-fixing discussions between me and Mick Andreas and Terry Wilson. And yet the government ended up indicting Mick and Terry, but they didn't indict Dwayne and Jim.

And why do you think that was?

Part of it was the way they did the investigation. Brian didn't give a crap about Randall, didn't give a crap about Dwayne. All he cared about was Mick.

Why?

My perception was he was jealous. Here was a guy of similar age. Mick was very successful. Brian's an agent in a one-man office in Decatur. He wants to advance his own career, but at the same time he wanted to bring down Mick, who he thought was a spoiled rich kid driving Ferraris and Mercedes and living in a big house by the country club. But don't get me wrong: I'm not saying this to vindicate Mick. He definitely fixed prices.

Did you ever try to report all these problems you were having with the FBI?

No. I know now that's because bipolar gives you poor judgment. You ignore things that aren't going right. I showed poor judgment in not leaving ADM when this whole thing started, in not getting someone at the FBI to listen to me about the briefcase incident, and in not taking my tapes to some internal affairs office.

Once you knew the FBI was ready to bring the case to a head, were you worried about your cover being blown?

Definitely. In the spring of 1995 I kept putting pressure on Brian Shepard. I said, "What if ADM finds out and my great career opportunity disintegrates?" You can't just find another job like this in Decatur, Illinois. So he said they would work something out where they would buy our house and they would pay my same big salary, which was $320,000 at the time, for a year or two, until I found another job. They never put it in writing. But I did tape those discussions, by the way. And later they called the deal off.

In June 1995, just days before the FBI raided ADM, someone from Justice advised you to get a lawyer, right?

Right. [Justice Department attorney] Robin Mann said, "You've done a fantastic job. Now you should think about getting an attorney." I said, "Finally. I've been talking about this for nearly three years." She seemed kind of shocked, because she hadn't been involved in any of those earlier discussions with Brian.

Did you get a lawyer?

No. Because she didn't make clear that I would need a lawyer before the raid. I thought she meant to just get one in the next few weeks.

So the raid happened on June 27 and blew your cover. How did that happen?

ADM said they were flying in the best lawyers from Washington to represent all the executives being questioned. So I met with a lawyer named John Dowd for four hours, and I made sure we had the proper attorney-client privileges. And I told him about being a mole. At the end of the conversation he told me he couldn't represent me because Robert Strauss, an ADM board member, was also a partner in his firm, Akin Gump. And by the next morning, a friend called and told me that Dwayne Andreas knew the whole story. I went into work, and ADM sent this junior attorney down to my office. He said, "Mark, you're not supposed to be here today." And ADM never let me back into my office. [Dowd wouldn't comment. He referred to a letter from a Decatur lawyer who said that he overheard Whitacre telling the ADM general counsel about "hundreds of tapes" after Whitacre's meeting with Dowd.]

I went to see Brian Shepard. I was pissed. I said, "Look, you guys. You busted up my career. You screwed up my whole life. I did this for you and you told me it was going to be some heroic action. This is bullshit. I did all this for nothing."

What happened next?

Iasked Brian to help me get a new lawyer. He called the U.S. Attorney's office and came back with Jim Epstein.

Ginger and I met Epstein the first time on June 30. But the night before I met Epstein, a friend at ADM called and said Jim Randall was telling people in accounting to pull invoices involving Mark Whitacre, that they were going to go after me for embezzlement.

What they're calling embezzlement was actually a bonus scheme approved by top management. And one of the tapes the FBI has is of Mick Andreas approving one of these bonuses for me, for $2.5 million. [Mick Andreas's lawyer, Jack Bray, denied this and all other allegations made by Whitacre.]

Anyway, I knew by early July that ADM was going to try to discredit me. It was the most depressing period of my life. There were some settlement talks going on between Epstein and ADM, where they would give me a severance payment and I would agree never to say anything negative about them. But ADM chose to go the route of discrediting me instead.

By early August, I knew ADM was going to bring up the embezzlement stuff to Justice. So I told the FBI agents myself. The next day, August 3, they told me the Justice Department prosecutors weren't happy. They told me the deal to buy our house and pay my salary was off. ADM was dumping me onto the street. And now the FBI and Justice were dumping me onto the street too. The world was falling through.

When did you think about suicide?

By Sunday, August 6, I started writing suicide letters. I wrote a lot of them. We had all our stuff packed up in boxes. We were planning to move to Tennessee. But we had to back out. Justice canceled the deal to buy our house, and I had agreed to freeze the money in my overseas accounts. Everything was crumbling.

I was thinking, "This case is going to drag on before the price-fixing case gets to trial. And now there was going to be a whole new investigation on the money stuff. And I'm more of a crutch to my family than an asset." So I decided to kill myself.

One of the letters I wrote was to Brian Shepard. I said: "You're the one who got me into this. You promised you'd protect me all the way through and told me I was doing the right thing. And you told me I was going to be a hero."

Did Shepard ever get that letter? No, my wife gave them all to my doctor. That was after my gardener found me slumped in my car, unconscious. My family drove me to this hospital in Chicago, one that treats a lot of executives. That's when I found out I was bipolar. I spent a week in the hospital. We decided to move to the Chicago area. By the end of the first week in September I had six job interviews. People have a tough time believing you try to commit suicide in early August, you get out of the hospital in mid-August, and by mid-September you have a job as chief executive of a company.

Why didn't you tell anyone then about your problems with the FBI?

Epstein knew what was going on, that I was pissed off about the FBI. But he just felt like, "God, you've got enough enemies. Let's hold this in the bag and not piss off the FBI." And you know, I got wrapped up in the new job. When I'd talk to reporters, I'd always focus on the ADM story because that was the battle at hand. You couldn't tell this story in one or two sentences.

So here you are now, four years after this all started, under indictment for price fixing yourself.

For what I did for them--I risked my life, my family, my career and everything--they should have given me immunity on everything. And to indict me on price fixing, that just doesn't make any sense.