"The crusades ended for me a long time ago. I don't know, I guess I never quite got used to the idea that all the things that I thought were aberrations -- the politics, the back-stabbing, even the petty little corruptions -- weren't aberrations at all. They're part of the system. Hell, they are the system."

-- Assistant U.S. Attorney Michael Holden in "Playing the Dozens"

"I believed it. I believed it all. I believed that judges were omniscient. I believed that lawyers were a higher order. I believed it for years and years and years and years."

-- Former assistant U.S. attorney William D. Pease, author of "Playing the Dozens"

A bulletin board hangs on the wall behind Bill Pease's desk, and the most prominent legend tacked there -- it would just haunt the peripheral vision of someone sitting at the keyboard of the IBM PC against the adjacent wall -- is a quote from Moliere: "Writing is like prostitution. First you do it for the love of it. Then you do it for a few friends. And finally, you do it for money."

William Pease is still in the early stages of love. But you get the feeling that his brain is papered with a whole range of unromantic warnings to the occupant: Nothing lasts. All is Vanity. Never presume. A man on the verge of a second successful career, a man already tired of being called the-next-Scott-Turow, a man who is hearing himself compared by reviewers to Dashiell Hammett and idol John Le Carre, the former prosecutor keeps the first copy of his book, the one the publishers sent him hot off the press, locked in a cabinet in his living room down the hall. As if it might split.

He did not weather almost two decades in the U.S. Attorney's Office in the District of Columbia by trusting his luck.

"The only way to describe this is: It was a fantasy," he says. "It was like being a child and thinking you're going to grow up to be a cowboy." At 47, after a lifetime of outgrowing fantasies, Pease has fulfilled his instead with the publication of "Playing the Dozens," a fast-paced, intricately plotted, Washington-based detective novel that has been highly praised weeks before its mid-September publication date. But he will acknowledge his pleasure only obliquely -- the same way he pursued his ambition.

"I didn't sit down, really, to write a novel," he says. He simply started writing -- scenes, characters, sketches -- in the early '80s, when (like his protagonist) he had 15 years as a prosecutor behind him. He had just finished the fraud and conspiracy prosecution of Mary Treadwell, Marion Barry's ex-wife, after a four-year investigation. He was working as a supervisor, as deputy director of operations in D.C. Superior Court, and he was up to his neck in office politics. "There were times when I just wanted to scream at people," he remembers. "So rather than doing that, I would come home and I would write sketches. I would just vent my spleen in some place where I wouldn't be held responsible for it."

Then, when he spent most of 1985 in the U.S. Virgin Islands on special assignment, he started noodling away at a plot. But still, in his mind, it wasn't a novel. "I fiddled with it, off and on," until 1987, when he quit the U.S. Attorney's Office in frustration. His divorce became final the same year, and as much as anything, he needed a way to justify to himself his desire to take a year off before starting another job. So he set up this office in his new house, and told himself he would Write a Novel. Like the kid and the cowboy, "you know it's never going to happen. But it gets you through the day to have this fantasy."

Even after he returned to the law, as a partner in a small firm doing white-collar defense work, he (obliquely) stalked his dream. Not that he was planning to get the novel published. "I thought all the way along that if I could just complete a story ... at least I could say I did it. Then the further and further along you get, you think, gosh, if I could just get somebody to read it. And then when somebody reads it and says, 'This isn't bad,' then maybe ..." His voice trails off.

If this air of indirection were less than genuine it might be infuriating. But Pease even seems to breathe tentatively. He's on the short side, with an apologetic smile and glasses half-rimmed in gold. He wears unflamboyant khaki trousers and a much-washed denim shirt, and the only two books he keeps on his desk are the tools of a man happy to ask for help: a paperback copy of Strunk and White's "The Elements of Style" and an enormous dictionary.

Until he wrote "Playing the Dozens," he says, "I never wrote anything, not even a letter to the editor." He corrects himself: "Legal briefs, which can hardly be called writing." This withering self-awareness is with him constantly, policing all his thoughts and words about the law.

But it is his experience that makes his book the good yarn it is. He worked as a line prosecutor and as a supervisor, tried federal cases and local ones; prosecuted murder and rape, cases of public corruption and complicated fraud. He is thus able to write with a pulpy authority about the lore of law enforcement: how an interrogation is conducted, the art of running a snitch, the impure pleasures of the game.

"The first meeting between prosecutor and defender is not unlike the rituals of a singles bar," he writes, "a dance of seduction between two rivals, each speaking with the voice of a virgin and the soul of a whore. The inexperienced or naive often find themselves pregnant before they realize they've been seduced: a defendant bluffed into a plea with an agreement to testify under the mistaken belief there is enough evidence to convict; a prosecutor dealing too generously too early only to learn too late that his star witness is more culpable than his target."

Having thus introduced an encounter between his prosecutor-hero Michael Holden and a former prosecutor now fronting for the drug lord Holden is pursuing, Pease writes that his characters "were neither inexperienced nor naive. They had lost their innocence years before and enjoyed the dance all the more for it."

This is where the fictional Holden differs from Pease, for whom the loss of innocence was no joy. He talks with a passionate disillusionment about his years in "the system," suggesting that for him, writing was a way of both leaving the law and coming to terms with it.

"The disenchantment comes from a system that in my view does not live up to the promise I thought it made. Whatever that means. It's watching sort of a systemic lack of care for the individuals who are involved in it. Where the system is more important than what the system was designed to do. The system is created by lawyers for lawyers, and it is propagated by lawyers for lawyers."

Once he sat on a committee that met every week or two, over a period of two years, to consider reforming the rules of jury instruction. As he recalls it, the group spent the time "quibbling over semicolons and colons... . No one ever sat down and said, 'Can we tell the jurors what they need to know, in language they can understand?' Because they didn't care."

Pease tried several famous cases in his career, including the 1983 prosecution of Treadwell and four associates and the 1974 prosecution of the three killers of Gail A. Cobb, the first female D.C. police officer to be killed in the line of duty.

But two less notorious cases stand like bookends in his memories, tokens of a career's frustrations. The first, very early in his career, was a prosecution for the murder of a cabdriver. Pease worked in the D.C. corporation counsel's office at the time, and the killer was a juvenile who, Pease recalls, "had robbed {the driver} and decided he didn't want a witness, so he killed him." The victim had left a widow and three children; the oldest child, as Pease recalls it, had to give up his plan to be the first in the family to go to college. So he felt a lot of satisfaction at winning this case.

"After the defendant was convicted and sent to Oak Hill, several months later the widow called me and said, 'I thought you told me the defendant was convicted.'

"And I said, 'Well, yeah, he was; in fact you were there at the time, remember?'

"She said, 'Well, I don't understand, he's standing outside my home.' So I made a dozen phone calls to find out what was going on, and basically, the answer came back, 'Well, you know, he was rehabilitated.' And telling the widow, 'Well, that's the way it is. The authorities have determined that' -- however many months it was, three, six; it was less than eight or nine months, and in my recollection, closer to four or five months -- 'that's the determination: He has really been rehabilitated.' It was a hard thing to explain to somebody. It couldn't be explained."

The other case was a fraud charge involving a pension fund, and Pease thought of it as "a lock," with two cooperating co-conspirators and a paper trail that traced the money from start to finish. In the face of such solid evidence, the defendants chose not to take the stand, rather than risk destructive cross-examination.

"Within a couple of hours at most," Pease reminisces, the jury comes back with a verdict: Not guilty on all counts. Incredulous, Pease and the detective who had worked the case approached the foreman after the jury was dismissed to ask what had happened. "You weren't fair," explained the foreman with some dudgeon. What are you talking about? spluttered the prosecutor. "Well, you let everybody else testify, you called all those witnesses to show what {the defendants} did, but you didn't let the defendants get up and tell their story."

A decade and more later, Pease still laughs a laugh that is more anger than amusement. "This is Lewis Carroll. This is the Queen of Hearts, this is crazy. You can't predict that kind of response. You're not allowed to say, 'By the way, it's the defendant's choice to testify or not -- you can't say that... .' Those are the things where you begin to learn how it really works."

He has especially harsh words for his former employer. He doesn't single out for criticism any of the several U.S. attorneys he served, but he recalls the early days of his career as a vanished time of decency. Earl Silbert, who served from 1974 to 1979, was, Pease says, "the best. ... He demanded case sensitivity, issue sensitivity: Are you doing the job to resolve the problem that we have? Not whether we've got forms to cover this. Not whether or not we are the biggest or the best. The case came first. The issues came first... .

"By the time I left, no one felt that way. It was like dealing with someone in a tax audit: 'But the regs say this. We don't care what the problem is. We've got a memo that covers that someplace. And if it isn't in the memo, if it doesn't fit the procedures, the hell with it. Because that way, we're always protected.' " Pease bites off this last word with some bitterness. "And then you get into these statistics. 'How many? We want to be able to show the court, and Justice Management Division, that we do more cases.' No one ever asked whether we were doing cases we shouldn't be bothering to do in the first place."

Eventually, Pease starts to blush, and mimes a search under his desk for a lost object. "God, where's my soapbox?" he asks. "I can't believe I'm running my mouth like this." But the loquacity lasts only as long as the questions stay focused on law or writing.

It comes to a dead halt when he is asked about his personal history.

"Mmnngggrrrrh," he says.

He is coaxed into divulging these bare facts: He went to college at the University of Maryland and to law school at Boston University. He is the younger of two sons. His father, an engineer, was an executive with a firm that sold industrial piping to power plants around the country. He grew up in Providence, R.I., and spent summers in his mother's native Durham, N.C.

This brief distance into his biography, he spies the barn door of digression, and bolts for it, trailing a disquisition on the differences between Southerners and New Englanders. He is confronted: Surely this diffidence is misplaced in a litigator, a former prosecutor who had a reputation, in legal circles, as a tough courtroom tactician? That's totally different, he says. "There, you walk in and -- it's Showtime! I was always nervous and shy, and when I was trying cases I'd, say, remember Jimmy Stewart in 'Anatomy of a Murder,' or Gregory Peck in 'To Kill a Mockingbird.' In court I'm acting being a prosecutor. It's not me."

Me is finding it hard to rise to the role of First-Book Author, Human Interest Story. "It's hard," he says. "For so long I worked to keep my personal life from my professional life." When a photographer arrives, his discomfort is complete. He poses in his dining room, but his is the suffering obedience of the dental patient.

The book is dedicated "To Anne, who bore the brunt." She is, he explains, his ex-wife. And yes, he says, the element of the novel that deals with strains on the prosecutor's love life did indeed borrow from his life. He talks about it -- indirectly. "You get involved in these things, and there is an element of, you think what you do is maybe more important than it really is. And it does tend to take over, at times... . It wasn't {one} case, it was -- for years, from one case to the next, getting caught up. It takes its toll. It did."

He lives alone now in the Foxhall area, in a house that is small yet still bigger than the limited spaces he seems to occupy there. The living and dining rooms have an air of suspension, down to the never-lit candles that wait in brass holders on the big table. Only the small study, with the packed bookshelf and the row of videotapes (yes, there are "Anatomy of a Murder" and "To Kill a Mockingbird") and the compact discs, appears fully lived in.

As if he had retreated here to fashion his new life. He has a second book contract, and splits his time, half and half, between writing and the law, one week on and one week off. "I don't think I embarked on all this as a means to get out of the practice of law, or to go away from it," he says. Writing, he adds determinedly, is simply "a wonderful sidelight that I really enjoy. I practice law to earn a living."

Listening to him rave about writing and rage about the law, you could be forgiven for suspecting that he is making his oblique, sidling way toward another ambition: the life of the full-time cowboy. "Maybe, God willing, maybe writing can be both my job and my love at the same time," he says.

"Maybe," he adds with characteristic caution, "maybe not."