I confess, I've only ever read John Grisham books on airplanes, and they have made those cramped, six-hour bicoastal flights at least bearable. Unlike Tom Clancy or his other best-selling competition, Grisham's publisher sets the copy with few lines to the page, spaciously typeset. The whole effect is to make the books seem light and effortless.

Yet, underneath, something pulses and burns. Grisham himself has never come across as especially moralistic, but his novels are intensely so; they are also deeply sympathetic to the vagaries of human behavior. In one, a young lawyer who is seduced by money and power realizes he made a devil's bargain and tries to do right ("The Firm"); another lawyer tries to determine whether a man who gunned down his daughter's rapists should be sentenced for murder ("A Time to Kill"); a lawyer journeys to the heart of the Amazon to find an heiress and confronts what truly matters in life ("The Testament"). In all these, his characters, usually morally neutral types at the beginning, get the chance to seethe with virtue as they decide between right and wrong.

Besides, Grisham's moral tone has been exemplary in the national debate, lacking Ken Starr's dogmatism, but maintaining a sense that some things are beyond the pale. In interviews recently, Grisham has expressed skepticism about the moral tone of the country, or rather about an absence of a moral tone. Grisham lashed out angrily at Hollywood for producing Oliver Stone's violent "Natural Born Killers," which apparently led to the copycat killing of one of Grisham's friends. Grisham, whose books tend to sell well as movies, has a voice in Hollywood, and his demand that certain lines not be crossed was widely discussed.

These recent expressions of dismay suggest that his disillusionment is deep. Nowhere is this despair more evident than in his latest, "The Brethren." The plot of "The Brethren" is straightforward enough. Three federal judges sit in a federal prison in Florida, serving time for crimes committed. One was caught embezzling; another killed two people while driving drunk; and the third was convicted of tax evasion.

These are the brethren of the title, and from their minimum-security lockup, they run a scam to ensnare rich men in a blackmail scandal. They place ads in newspapers around the country, representing themselves as a young man in distress; after several letters back and forth, they get a private investigator to find out the identity of their pen pal, and then they threaten to expose him to his wife and family unless he pays. The scheme works too well, and they hook a United States congressman.

Congressman Lake is no run-of-the-mill backbencher. He's the front-runner in the 2000 election, and he's running on one message: double America's defense budget. He has one strategy: fear. And he's only running because the director of the CIA, a front man for the military-industrial complex, has chosen him as the most innocuous, pliable candidate. But Lake has a secret vice, which the brethren inadvertently tap into, and which the CIA director discovers.

Midway through the book, the moral denouement ahead seems predictable. The brethren will expose the candidate but get their comeuppance in the process. But Grisham takes a uncharacteristic turn, toward moral ambiguity. The brethren win out in the end; so does Lake, and the CIA. In fact, there is no moral payback, because there are no clear heroes and no clear villains (though the CIA chief is eerily and utterly without redeeming qualities). With grim resignation, Grisham allows Lake to win the presidency; money to dictate elections; and blackmail to get his crooked tribunal out of prison.

Grisham seems to have thrown up his hands, as if to say, what's the point? It's a strange turn for the writer we've come to look to as, if not a moral beacon, then a bright thread in our cultural fabric. The disillusionment, temporary or not, of one of the most widely read writers of the past decade mars his effectiveness as a writer. Tales like this need a clear moral lesson. Grisham's resignation is a short step from cynicism, and not a particular illuminating sort of cynicism.

Grisham's trajectory seems an allegory for an era when even moral ambiguity has little traction, an age when success is defined by income, and vision seems to be measured by stock options. But no matter how challenging and dispiriting it may be to wrestle with unpopular questions, our only other option is to say, "Whatever." Grisham seems to have taken the latter road; let's hope he realizes that it leads nowhere.