The Boorn Conspiracy : THE COUNTERFEIT MAN: The True Story of the Boorn-Colvin Murder Case. <i> By Gerald McFarland (Pantheon Books: $22.95; 242 pp.)</i>

Be it police procedural, Simenon-style psychological, hard-boiled Chandler atmospheric or Marple-flavored deductive, there is one thing you usually can count on in a murder mystery: a body. In the tale of Russell Colvin, though, there is no body. There might not even have been a murder. But there are plenty of people doing and saying strange and suspicious things, and there is certainly plenty of mystery.

Its Cold War-thriller title notwithstanding, “The Counterfeit Man” is historical nonfiction--the latest in a long line of pamphlets, books and articles (McFarland cites nearly 30 of them, not counting newspaper pieces and manuscripts, in his bibliography) about the strange case of Colvin, who may or may not have been slain in Manchester, Vt., in May of 1812.

The story is simple on the face of it: One morning, Colvin, a down-on-his-luck sometime farmer, was seen arguing in a field with his brothers-in-law, Stephen and Jesse Boorn, while his own young son looked on. After the dispute, Colvin vanished. The Boorns subsequently were accused of murdering him, and, though a body never was found, convicted. Both men were sentenced to death, with Jesse’s punishment later reduced to life imprisonment at hard labor. Then Colvin reappeared, and both men were released.

Where, then, is the mystery? To begin with, the Boorns were not brought to trial until seven years after Colvin’s putative murder. Indeed, his disappearance was not a matter of great concern to the community at large: His economic and social standing were low, and he was by all accounts an odd man, described by contemporaries as “at times insane” and “very simple and ignorant,” and known to wander aimlessly around the countryside, on one occasion disappearing from Manchester for almost nine months. Even his wife Sally--the Boorns’ sister, herself known for frequent trips “out of town” and for what McFarland delicately calls “her own independent network of friendships”--did not seem overly concerned with Colvin’s absence.

The Boorns finally were called to account only after Manchester had been riven by religious feuding, Sally Colvin had been denounced for immorality and Colvin’s ghost had reportedly been sighted by local citizens in numerous dreams and visions. One of the tasks McFarland--a professor of history at the University of Massachusetts--sets himself is to discover what it was about Colvin, the Boorns and Manchester itself “that shaped the public’s response in such a way that an official inquiry into Colvin’s disappearance was delayed until 1819.”

McFarland’s other main concern--and this question has been at the heart of nearly everything written about the Boorn-Colvin case for the past 170 years--is to determine whether Colvin really reappeared at all, or whether the returning vagabond was in fact a clever impostor, a counterfeit. (An obvious if only partial parallel here is the case of the 16th-Century pretender Arnaud du Tilh, who impersonated a French villager named Martin Guerre in order to enjoy the benefits of his estate. In the Du Tilh case, though--which was dramatized in the 1983 Daniel Vigne film “The Return of Martin Guerre,” starring Gerard Depardieu--Guerre was in fact alive, and returned to set matters straight.)

In attempting to unravel these mysteries, McFarland tells us a great deal about life in north-central New England in the first part of the 19th Century--complete with demagogues, libertines, swindlers and even purported vampires--and a very great deal about the various Boorns and Colvins and their relatives, associates, enemies and friends.

And he reveals a delicious irony: Whether or not the returned Colvin was a counterfeit, Jesse Boorn turned into a real counterfeiter, the kind who replicates money, years later in Ohio, and apparently confessed to a supposed confederate named Hackett that he and Stephen had indeed murdered their brother-in-law and then found a substitute Colvin to fool the authorities. Unfortunately for Boorn, Hackett turned out to be an undercover deputy U.S. marshal, and though Boorn successfully denied that he had confessed to Colvin’s murder, he did serve five years in prison for his counterfeiting.

But has McFarland then solved the Colvin mystery once and for all? Not really. All he finally tells us, in the book’s awkwardly phrased final sentence, is that, “To be sure that Colvin was an impostor cannot be established for certain; but at the same time, one can no longer dismiss out of hand the possibility that, in what he said to the seeming outlaw Hackett, the counterfeiter Jesse was, for once in his life, telling the truth.”

It seems to me that we have persevered through an awful lot of painstaking detail by this time to end up with so equivocal a conclusion.