The Assemblers by Speer Morgan (Dutton: $17.95; 278 pp.)

I almost hate to disclose that the plot of this uneven, yet entertaining mystery involves computer fraud. But, of course, the title itself is a clue ( assembly is the primary programming language of a computer), and the jacket design and text make it apparent that this book involves computers.

Don’t let this scare you off. You don’t have to know anything about computers to follow the plot. The more you do know about them, however, the more you’ll appreciate the intricacies Speer Morgan has dreamed up.

Ray Weil and his estranged wife, Bobbi Reardon, are cops in a backwater Arkansas town where the principal employer is a company called DataForm, headed by Wayne McNear, an ambitious man with a clouded past.

The plot twists may be very high tech, but the sinister setting is starkly familiar--small town, monolithic power structure, a few decent folks worried mostly about their own personal problems, a few oddballs. Insularity pervades everything. You just know that some of these good ole boys aren’t.

The story opens with the discovery of Ben Mitze dead inside a trailer stuffed with computer gear and hidden in the Arkansas woods. He’s been working at a terminal. The words on the screen make no sense to those who investigate. Not until the end of the book do we learn what he was doing and why he was doing it naked.

Morgan, director of creative writing at the University of Missouri who has published two previous novels and is editor of the Missouri Review, needs a good editor himself. It is sometimes a struggle to follow the action because his writing is unclear.

A critical turn in the plot comes when Reardon leaves the police force to join the security force at DataForm. Describing the events leading to this, Morgan in one paragraph places Reardon at the head table at a Kiwanis Club luncheon where McNear is the speaker. The next paragraph goes like this:

“The idea was to give her a chance to get further acquainted with DataForm by meeting Ron Reed, security chief, and hearing the talk. Mr. Reed had spoken with her briefly and unrevealingly before driving them all over. He was a big ugly man with greased-back hair and an open top button on his shirt, where he wore a gold medallion bigger than a silver dollar.”

At the beginning of the very next paragraph, we find McNear sitting in the back seat of a car. Is it after lunch already? Nope, must be before because two sentences later, we’re in a jammed dining room. And what do you think of the funny way Reed wears his medallion up around his neck? Maybe they can’t afford long chains in Arkansas.

These are hardly fatal flaws; they are just the ordinary rough spots of a first draft. Frankly, you expect better when a reputable publisher puts those paragraphs between hardcovers and expects you to pay $17.95 to read them.

Surprisingly, it’s when Morgan presents the computer aspects of the plot that he seems most lucid, which is a blessing because the story would be very hard to follow if he had not so skillfully woven in the elements of computer crime.

It is obvious to the reader from the beginning that some kind of computer crime is being perpetrated, but the nature of the crime and the identity of the criminal remain a mystery. The suspense builds as we discover that major banks are losing their computerized accounting systems, banks that are clients of DataForm, whose business is ostensibly to provide security against computer crime.

Lurking not far in the background are: USI, the fictional dominant computer manufacturer in the country; the National Security Agency; a powerful satellite of a secret design through which the bank computers are being manipulated; and--murder.

Then there are Ray and Bobbi, fighting each other in a bitter divorce, quarreling over the behavior of their 16-year-old son, yet each needing help from the other as they separately begin to unravel pieces of the puzzle.

Both are wily and intelligent in their own ways. Each begins to discover how big the conspiracy is and how high the odds are stacked against them to do anything about it.

You don’t have to understand anything about computers to know that that’s the stuff from which good mysteries are made. Once you’ve finished this one, I think you’ll agree that first draft or not, Morgan has delivered a good mystery.

I just hope he gets a real editor next time.