It is 1960. Senator Kennedy and his beautiful wife are living on N Street. God's in his heaven, all's right with the world.

Jake McKay is a freshman at Georgetown, sensitive because of his crippled leg, or at any rate sensitive about his crippled leg. In the name of Sen. Kennedy and his new decade, Jake stands up for freedom. He refuses to wear his beanie. He gets hazed by the sophomores.

Jake's father is CIA. Ex-OSS. Jake's English Uncle Giles was his father's partner in an undercover adventure in occupied France. Uncle Giles is exquisite, but he is gay, and a mole.

The day things begin to go wrong is the day Jake goes to the Phillips Gallery and falls in love with a girl. She looks like a Degas bronze, and he doesn't even dare speak to her.

Her mother appears, cool and blond. Then a man, who gives the mother a rose. She kisses the man.

"Jesus Christ," says Jake. It is his father.

James Carroll can write. As the French say, he has the lion's paw. He can build a story, pace it, twist it away from your hand just when you think you've grasped it.

The opening chapters of "Family Trade," his fourth novel, are masterly. He has evoked a place, a time, a mood, a moral atmosphere. He has tied a cluster of people together in a knot that binds them so tight it cuts them all to the flesh, a knot your fingers must unravel.

In those first chapters his people are solid, believable, they get up and walk, or limp, around on their own. But they also have an aura. There is a mystery linking them together, a mystery not in the banal sense that poeple talk about a "mystery novel," a mystery in the metaphysical sense.

The key to it lies back in the past, in 1945, the year the world we live in began with two big bangs and a lot of whimpers. That was when Jake's leg was crippled in the Blitz, and that was when his father and Uncle Giles went off together on no ordinary mission, and the knot was tied.

The resolution, or the unraveling, does not happen until 1980. But it would be wrong to spoil the plot. It is cunningly devised and skillfully worked out. And it held me to the end. I finished it on a train from Oxford to London, and when the train reached Paddington station in London I sat there, long after the other passengers had left, because I had to know what happened on the last page.

It is so good that it deserves to be judged by higher standards than those of just another clever mystery novel. For one thing, at his best Carroll writes so well that he couldn't write "just another mystery story" if he tried.

He has the real novelist's gift for creating a situation in which the characters respond, not as the writer makes then respond, sentence by sentence, but as they must respond, because of the way he has already created them.

Then again he is clearly trying to do something more than entertain. He is telling us something about America: about the United States and Europe, but also about innocence and the loss of it. It is not just Jake's loss of innocence that has its beginnings in 1945.

Judged by serious standards, then, I thought "Family Trade" didn't live up to those brilliant opening chapters. A small thing shook me first. It is the very first sentence of the second section of the book.

"Group Captain Patterson"--that is Uncle Giles, and he is driving through the English countryside in 1945--"drove with his left arm stiff, a strut between his shoulders and the wheel, while his right hand rarely left the polished knob of the gearshift."

I tried it for 10 minutes, twisting myself like a contortionist, until I got it. Carroll thinks that people in Britain drive on the right-hand side of the road. They don't. Silly of them, of course, but they don't.

In the same way, it is silly of the Germans, no doubt, to make the word "catastrophe" a feminine noun, like the Greeks did, but there it is, they do. They don't say "Das Katastrophe Kommen," for "the catastrophe is coming"; they say "die Katastrophe kommt."

Those are just two examples, utterly unimportant in themselves, of the way the English and German characters in the book are made to say things they never would or could say. It doesn't matter at all that no Englishwoman would ever talk about the "pits" in her tangerine, she would say "pips." Nor does it matter that no Englishman in the 20th century would address someone as "my man" or say "whomever."

What matters a bit more is that characters are made to say things that are historically untrue and psychologically implausible. Can you imagine an educated German, for example, saying, "They have the best equipment. American, naturally." In 1980!

Nor can I very easily imagine an Englishman, who has flown with the RAF in World War II and been parachuted into occupied France, speculating that his German and American friends had more "substance of character" than he because they were German and American! There is chauvinism lurking in some of the naive contrasts drawn between "innocent" Americans and "corrupt" Europeans. There are corrupt Americans, too, and innocent Europeans.

Carroll writes so intelligently about Washington that it is a shame he did not research the European background of his story with more care and sympathy. His Berlin is a mere studio set, glimpsed from a tour bus. He calls it "the world capital first of imperial adventurism, then of cultural decadence, then of racist militarism." If only it were as simple as that! Berlin was the capital of other things, too: of Einstein and Schoenberg, Max Reinhardt and Bertolt Brecht, of assimilated Jews and social democracy, of modern mass media and the first golden age of the movies.

Carroll's England is an even more shadowy place, and the motives of his English mole are implausible. Certainly they are very different from those of the real traitors, who went East not out of Weltschmerz, but out of ambition. They wanted to be on the winning side, but guessed wrong.

All of which only goes to say that I want more James Carroll, not less: his great gifts should not be thrown away, as in part they are in this book, on too shallow motivations, and too melodramatic situations.