Cassidy by Morris West (Doubleday: $17.95; 282 pp.)

It’s comforting, ordinarily, to put your trust in something--the national government, say, the rule of law, the goodness of God, love itself. One would have been wise not to bank on any of these with the late Charles Parnell Cassidy in the picture. Labor premier of Australia, brilliant tax attorney, bosom friend of Irish Catholic cardinals, Cassidy was pre-eminently a confirmed pragmatist in all things. To apply the minimum of law while allowing the fullest interplay of society’s natural forces was Cassidy’s idea of a good balance, indeed, and he was fondly wedded to the “ugly proposition that the human animal is infinitely corruptible.” True to such dictates and before the very eyes of an admiring public, he had, with fine panache, corrupted whatever he had touched.

Or, it is better to say, so it later appeared. Where Cassidy was concerned, certainty was elusive. There was, you see, that vexingly contradicting side to him, that “taste for paradox.” The safe opened after his death contained, it is true, dirty money, dirty pictures, a loaded .38 and a kilo of heroin. But it also held directions to disburse a considerable portion of his ample millions to the church. Is anybody altogether bad?

Come to think of it, is anybody altogether good? That the worrisome part, and readers familiar with one-time seminarian Morris West--the adroit storyteller and painstaking researcher of so much best-selling fiction--will recognize in his latest a book of coloration distinctively Western: the perplexing imprecision of morality in a world where the ambiguities wink beguilingly beside the frowning old verities. Surely in the way West has constructed Cassidy’s moral makeup, the line between legal and illegal, ethical and not-so-ethical, is an untrimmed hedge of equivocation and expediency.

Martin Gregory, a knowledgeable British jurist who had learned his law at Cassidy’s paternal knee--but had had the alienating nerve to marry the boss’ daughter against his will--narrates the story of his manipulating father-in-law. The time is the recent past in Australia (West’s native land), and Gregory’s account is filtered through the eyes of a man who has been summoned out of exile. On the brink of his cancerous death, Cassidy, the head of the government, asks Gregory to be the executor of his extraordinarily convoluted and suspect estate. Has all been forgiven? Is Gregory being tested? Set up? Well, hard to say, but the overriding question Gregory is obliged to ponder--the sardonic nickname Cassidy applied to him was Martin the Righteous--is whether one can combat evil without resorting to it. Is one ever safe from “the traitor inside?” The answer he at last arrives at is a remorseful no.

It is not, after all, your everyday last will and testament the premier leaves behind in Sydney. It is more on the order of an open-at-your-own-risk parcel of sinister international crime. Bribery, blackmail, drugs and murder were included in the coinage, and the net worth, conservatively, is half a billion dollars. With the assistance of the Australian Federal Police, Gregory is of a mind to clean house, but his hunch is that unless he is cagier than even Cassidy himself had been, the whole thing may go off at any moment and do him in. What was the dictum Cassidy liked to recite when he and Gregory had lovingly practiced law together (and before Cassidy lost his daughter to his protege)? “Never get mad, get even! Remember Shakespeare: A man can smile and smile and still be the son-of-a-bitch he wants to be.” Funny, isn’t it, that as Gregory maneuvers warily through the dead man’s legal and financial indiscretions, he keeps being reminded by others that he’s “just like Charlie Cassidy” himself?

Where it might have been said that in his day, Cassidy was cheerfully, almost endearingly, venial, his surviving partner in shady dealings, Marius Melville, is more forthcoming malevolent. With an icy eye to a financially secure old age, he does not scruple to insinuate himself behind the executorial scenes, the better to edge Gregory toward hasty, injudicious decisions. And while, given the time and the room, there were no likely limits to Melville’s instincts for mayhem, neither compromising sexual by-plays nor murder itself quite suffice to divert Gregory from his fiduciary duties. As recompense, though, (and, not incidentally, to save his own skin) Gregory the Righteous is to have the tempered satisfaction of seeing Melville, Satan-like, fall like lightning from the sky. His moral pain is in having to admit that he, too, can employ violent processes.

West calls his novel “a fable” not to be taken as history. Fair enough; I hadn’t thought to. Moreover, as Aesop demonstrated, fables are commonly peopled by animals. So it’s OK that “Cassidy” is not without a few horsefeathers. It’s burdened, too, by not just a little financial and legal parlance (the fiscal authorities surely “will try to inglobate all assets,” we are told along the way), and that means it’s not only Gregory who must pick through the tedium of testacy. Finally, West’s own stature is diminished by the book’s casual sexism, and whether we’re seeing the protagonists’ or the author’s boorishness showing through, it’s repellent.

Setting these matters aside, “Cassidy” is something more than an involving exotic, cleverly put- together thriller. That’s not just because Sydney, Australia, is such a very unlikely place in which to find yourself, either. “Cassidy” is worthwhile chiefly as an encounter with situational ethics run amok.