BOOK REVIEW / In deadly pursuit of uneven, foggy margins: 'Body of Truth' - David Lindsey: Warner Books, 8.99 pounds

WHEN is a thriller not a thriller? David Lindsey's last novel, Mercy, was a long, thudding shocker about sex crime. It did not leave much to the imagination, and seemed to have no aim other than to give us the creeps. But this new book is several degrees more ambitious. Indeed it is a rather thorough and striking example of the way thriller-writers have parked their tanks, as it were, on the neat lawns of polite literature. Not only that: they even have the nerve to wave the gun turrets around and loose off a few salvoes towards the deckchairs on the patio.

Ostensibly it's a man-hunt - or woman-hunt - set in Guatemala. A rich American girl called Lena has disappeared while working for the Peace Corps in the Guatemalan hills. Looks like she uncovered some scandal, maybe something to with the vicious General Azcona, whose wife has been kidnapping the orphans created by Azcona's troops and exporting them to sentimental new parents in America and Europe.

A detective called Haydon is engaged by the family to check things out. Almost at once, he loses himself in a growing tangle of distortions and lies. The plot - Where's the girl? What was she up to anyway? What's the difference between the good guys and the bad guys? - merges with the movement of the book's thoughts on political morality. There is even a lengthy conversation between Haydon and a revolutionary doctor about Heinrich Boll: 'Boll said that, at bottom, truth was an 'assembled' thing. It could not be found in one place.'

The best thing about Body of Truth is that, as the pun in the title suggests, these philosophical digressions are not merely tacked on. The book opens like this: 'Haydon stared out through the rain-spattered windshield of his car, past the uneven, foggy margins that had formed around the edges of the glass in the cold January afternoon, and waited for the woman to gain control of her emotions.' It is, as a thriller should be, precise and immediate. But it is also quick to whip out the novel's main idea: that life has 'uneven, foggy margins' which stop you from seeing things.

A chapter or two later, Haydon is sitting at home. No ordinary detective, he is listening to the Messa per i defunti by 'Giovanni Pierluigi da Palestrina' and doodling over a translation of Giacomo Leopardi's Pensieri: 'He stuck with it, battling verb forms, wrestling with the baffling rules of grammar and grappling with a system of sentence structure that seemed to fold back over itself.'

The lofty references seem a bit out of place in such an aggressive ('battling . . . wrestling . . . grappling') context. But perhaps because this is a book in which people really do wrestle and grapple, the figures of speech do not seem fanciful. And because Body of Truth is also blood- spattered, they have not sprung from anyone's ivory tower. In any case, this is a detective who is soon going to be chatting about Heinrich Boll and the nature of truth, so he needs to be educated. And it is nice to see that stealthy reference to structures that fold back over themselves. There are many such images of confusion and deception.

This extends to the way the characters are pushed around. Haydon's first encounter is with an old mucker called Cage, now a dangerous loose cannon with connections in all the highest and worst places. With characteristic breadth, and in perfect keeping with the book's prevailing thoughts, Lindsey describes him with a punchy series of contradictory qualifications. 'He was a habitual liar, self-centred, incapable of empathy, without conscience, full of arrogance, devoid of malice, as calculating as a chess master, undeniably charming, and as possessing of true bravery as any man Haydon had ever met.'

As Haydon moves through the swarming, blood-stained streets of Guatemala City he keeps encountering different angles on all the characters. The revolutionary doctor seems to be a modest and high-minded liberal, but Cage sees him differently: 'A little rich fart who's playing at this business of 'internal struggle'. He's the worst kind. He dabbles in it.'

The same goes for Lena. At first she's a saint: 'a champion of poor people, a freedom-fighter for moral causes'; but then we learn that 'she has screwed her way from one end of the Central American isthmus to the other, that she is cunning, conniving, and a user.'

Guatemala itself has Lindsey's sympathy: 'The generals were busy executioners who preferred to use a new blade every time they lopped off a head. And they wanted the latest in blade refinements, too, the ones with the brightest, most technologically advanced edges. So the blade salesmen came from all over the world . . . The executioner was busy, the blade salesmen were busy. There was a good living to be made . . .'

This is good strong stuff. Plenty of more pretentious novels have refused to deal in such equivocations, and have flinched from looking close up at guns- in-the-face brutality so as not to seem like thriller-writers.

But by the end it is hard to know which is the stronger of the book's two engines. The plot starts backfiring as it reaches its climax, as Haydon moves in on the girl; and the final irony is delivered in a rather drab postscript. Meanwhile, the existential ironies - the fragmented nature of truth, and so on - are warming up. 'Truth was an assembled thing,' Haydon thinks, remembering Boll, 'unknown to a single person, non-existent in a single ideology. It was more difficult to grasp than expired breath, more complex than the simple desire to possess it.'

This might well be true, but it's not much of a way of saying so. Truth, in this determined language, is about as mysterious as a missing person: it's out there somewhere, holed up, but the cops will probably bring it in for questioning any day now. Body of Truth is least effective when it is most assertive. Otherwise, it has plenty going for it.