"IF YOU CAN'T STAND THE HEAT," some of the hardnosed characters in Henry Allen's very good novel about sex, death, and intrigue in Washington are fond of saying, then "stay out of Nagasaki." Or Stuckey, Maryland, for that matter.

According to a tattered 1971 edition of The World Almanac and Book of Facts, there is no Stuckey, Maryland, although Allen assures us it is the "mean-dog and used-motorcycle capital of the world" populated by "men who were proud to stand up when they worked and women who liked to turn the lights out when they made love." I can only conclude that the almanac is wrong and Allen is right.

Named no doubt after members of the dynasty who founded that rash of godawful pecanroll joints which fester along the interstates, Stuckey is where Gordon Sault, ex-Vietnam Marine, ex-newspaperman, ex-Senate aide, ex-everything, lives a life of desperate quietness in a 1938 pre-fab Sears bungalow until he meets Ellen Cane, the quintessential golden girl. After that, Sault's life becomes an exciting mess of violence, death, sex and scandal in approximately equal proportions.

Ellen Cane's father, a resident of Foxhall Road, which immediately signals almost all we need to know about him, was once an OSS-CIA operative who lucked into a job at the White House as a high-ranking aide to John Kennedy. It was there that John Cane came up with the cute idea of cooking the nuclear books.

It was a devilishly simple scheme. Just juggle the figures to make a few hundred pounds of plutonium show up missing and probably stolen at inventory. Let the information leak out and it would turn into a political wild card. As Cane explains it to the Senate committee he's been hauled up before, "The gist of it was that in a world in which no one would actually start a nuclear war, we could give everyone the opportunity to bluff, thereby bringing all the benefits of nuclear stalemate to the underprivileged."

But not everyone buys Cane's glib explanation. In fact, there are murmurs of treachery and even treason. To buy himself time and public sympathy, he arranged to have his daughter kidnapped by an over-the-hill wire man who once bugged Cane's wife and John Kennedy in some indelicate act. But the scheme backfires and Cane calls on Gordon Sault to find and, if need be, rescue his daughter.

Riding into this scene in a clapped-out Chevrolet Malibu are two Middle East terrorists, bent on finding out if Cane perhaps really did squirrel some plutonium away. One is a Maalox-gulping killing machine called Carlos, which is not a bad name for a terrorist, and the other is the delightful bumbler, Farhad, "the eternal schlemiel, a gourmand of second chances who . . . had come completely unglued the instant he hit the USA; who had stuck up a Pancake Palace in Hollywood Park, Florida, to get quinella money for the greyhounds; who had caught the clap twice at the same massage parlor in Beaufort, South Carolina; who had mailed back to Teheran six matching sets of white plastic loafers and belts," and so forth.

The people who hang out with Ellen Cane come to bad ends. They are shot, stabbed, and pushed into rivers. Allen, through his considerable skill, is able to make her both attractive and reprehensible by climbing inside her skull where all the neuroses writhe. We also understand how she might have got that way after her father tells her why she should appear to be kidnapped: "If the rest of the world thought you were missing, fine. Maybe it would remind them that I'm more than some hit man in pinstripes, I'm a father, too." With fatherly advice like that an offspring's therapy bills can only be astronomical.

Although Allen succeeds admirably in fleshing out his protagonist, Gordon Sault, he does even better with the aging wire man, Eddie Conchis, who drives a burgundy Coupe de Ville and wears honest glen plaid suits and honest wingtipped shoes. Honesty plays a large role in Eddie's life. "It was the price you paid in this world," he figures. "Eddie's specialty was honesty of the negative- virtue sort: no bullshit. He suspected he had the field to himself."

As a writer, or perhaps even a stylist, Allen (a reporter for The Washington Post) is impressive. He has an excellent ear for dialogue, reminiscent of John Gregory Dunne and the early George V. Higgins, but without Higgins' sometimes irritating tape-recorder effect. And best of all could be Allen's remarkable eye. He sees well and remembers better. Almost any passage will serve: for instance, this one about Georgetown, which explains why Gordon Sault prefers Stuckey: "There were bay windows, brick sidewalks, magnolia trees, and brass plaques, shined daily, reading TRADESMAN'S ENTRANCE. There were slate roofs, antique fire-company blazons over burglar-alarmed front doors, gas lamps lit all day, and serpentine walls, all of it looking a bit too precise, as if it were merely a scale model of a real Georgetown that was much larger, infinitely large, heaven itself."

Although Georgetown, or Perfectville, as Sault calls it, has been burnished to a high gloss, the plot of Fool's Mercy might have used a bit more tinkering. A twist of a wrench here, a drop of Three-in-One oil there. I had trouble with the machinations of the ex-Camelot knight, John Cane, but then who knows what the denizens of Foxhall Road are really up to.

Allen has written a splendid sexy thriller which is also a fine book about Washington that recognizes it as a real city with strange dark corners into which the author has poked most skillfully.