FOXCATCHER. By William H. Hallahan. Morrow. 321 pp. $16.95.

ON Page 235 of William H. Hallahan's new thriller, Foxcatcher, he refers to "downtown" London, rather than the more usual "Central" London. That is the only false word in the novel. Foxcatcher is the best thriller I've read in years.

Standards for the thriller are pretty high -- at the top of my list are Harry Patterson/Jack Higgins and Elleston Trevor/Adam Hall -- but Hallahan, author of The Search for Joseph Tully, Catch Me: Kill Me, and The Trade, among others, matches the best of them with Foxcatcher's bare- knuckles action and bare-bones prose. His characters are not bulletproof supermen but super-skilled human beings, trained to do a job that almost every one of them has come to despise. His research alone builds the kind of suspense that reminds me of the tension in Thomas Harris' Red Dragon, and the portrait he paints of the world of international intrigue -- State Department politics, the value of favors, the daily deceptions and betrayals, the constant fear, the daylight paranoia, the deadly loss of humanity -- are as crushing and as bleak as anything in Deighton or le Carr,e.

The focus is chiefly on two men. Brewer is an ex-CIA agent doing nine years in prison. He was framed and betrayed by the Company, but he doesn't know how or why. Even more mysterious is his sudden release . . . and the threat on his life . . . and the invitation to treason. The other man is McCall, a highly-placed agent, tired of late nights and rooftop fistfights, as disgusted with the memory of screams he's heard as he is by the new murders he's planning. Then there's the Iranian agent who needs computer parts and for whom price is no object. And there are the three international arms dealers who care only about price. Hallahan weaves these lives together so tightly that the pages of the book almost turn themselves.

Filled with non-stop action, this is also an introspective book. McCall, who had planned to be sailing on Chesapeake Bay with his son, wonders, "How in the world had he come to this empty room on this bare floor, in this unused building, to stalk a fellow mortal with the avowed purpose of having him murdered?" And the chilling, muted ending -- complete with a breathtaking revelation -- strikes dark chords that sound like Mahler turned to prose. Wisely, Hallahan does not explain all the questions raised along the way, with the result that, hours after finishing the book, the answers go off like gunshots in your mind. CYCLOPS. By Clive Cussler. Simon and Schuster. 475 pp. $18.95.

IN Cyclops, Clive Cussler details the latest exploits of his intrepid hero, Dirk Pitt. Remember Dirk? Remember Raise the Titanic? Well, that was nothing compared to Pitt's recent activities. Nothing.

This time out, Cussler performs a frenzied juggling act with plotlines. First, it seems that a secret organization years ago placed a colony of Americans on the moon. The colonists are due to come home soon, and not even the president knows about it. That's one plot. Then there's the plot involving Fidel Castro's friendly overtures to the United States just as the Russians in Cuba are planning to get rid of Fidel in a pretty colorful (and loud) manner. And then there's the plot involving a fabulous sunken treasure which is actually -- get this -- the fabled wealth of El Dorado.

Never mind that the dialogue is made of solid oak. Never mind that you could read this review right through the characters, so thin are they. Never mind that Dirk's vaunted wit is only nasty sarcasm. Never mind that the proofreading is atrocious. The plots fly fast and furious, Dirk never disappoints, and the photo of Cussler on the back of the book is worth the price alone. THE LeBARON SECRET. By Stephen Birmingham. Little, Brown. 403 pp. $17.95.

I AM NOT A good candidate for gossipy novels about the wealthy, but I've just finished Stephen Birmingham's The LeBaron Secret and, let me tell you, it's terrific.

Septuagenarian Sari LeBaron runs the San Francisco- based and family-owned Baronet Vineyards with an iron hand that she doesn't even bother to conceal in a velvet glove. She's one wily lady, and now she faces a takeover bid led by, among others, her disgruntled son Eric. But the drama of the takeover bid is nothing -- I mean, nothing -- compared to the family dramas that it unravels.

What of Sari's lifelong friend and sister-in-law, Joanna, equal owner in the business and co-holder of at least one terrible secret? What of the rivalry between brothers Eric and Peter? Why is daughter Melissa sponsoring a sleazy rock star? What part will be played in all this by Gabe Pollack, possibly Sari's only true love? How did Sari's husband die? What about the gruesome walnut trees in the graveyard? And what about that mysterious trip to Europe half a century ago, what about that? And is it really important, as Sari has wondered all her life, to be in love?

Birmingham writes with honest love for his people, forgiveness for their weaknesses, and a hard edge of bitter reality. He gives us a good long look through an open window, and provides plenty of opportunities to slap the arm of your chair and mutter, "I knew it! I knew it!" HEARTLAND. By Robert Douglas Mead. Doubleday. 636 pp. $22.50.

THE LATE Robert Douglas Mead won praise for his previous novel and several works of nonfiction. His final novel, Heartland, is likely to win more. It is a lengthy retelling of his own family's history in settling the West at a time when, in the 1850s, that word meant to most settlers the rich and unclaimed prairies of Kansas.

Young Isaac Pride setsut to find gold at fabled Pikes Peak in the Colorado Territory, but bad luck and discouraging tales cause him to stop midway across Kansas. There's plenty of land to ride and plenty of buffalo to shoot and, slowly, Pride begins to build his life, his world growing richer in every sense as the country itself expands. And always, the challenges grow in number and intensity. Much of Mead's writing here is vivid and his love for the land intense. His descriptions of the plains, for example, and of buffalo hunts, have a kind of wide-screen clarity. But in some ways, the personal nature of Mead's material has betrayed him. These family tales are richly detailed and filled with a reverence for traditional American values, but they seem rather to exist in a vacuum. We may live our lives day by day, but we expect an historical novelist to present a larger context -- what were these times like? how did people think? what else was going on? -- than Mead supplies here. FINDING HOSEYN. By Colin MacKinnon. Arbor House. 306 pp. $16.95.

"TRUTH," Colin MacKinnon writes in his first novel, Finding Hoseyn, "was a dangerous and valuable commodity. You had to mix it with something else to cut it, like putting powdered milk in heroin."

MacKinnon, a Washington journalist and editor of Middle East Executive Reports, is writing about Iran. He spent some years there and he knows his subject.

Finding Hoseyn is a thoughtful thriller about an American journalist in Tehran in the last days of the shah. Good news stories are hard to come by -- and even harder to believe -- so when Jim Morgan spots some oddly related circumstances (a terrorist murder, a story suppressed, and a fellow journalist expelled) he figures he's Onto Something. Pursuing a story in the Middle East, however, especially when you don't know where you're going, is not easy. His path, blocked at every turn, is tangled with contradictions and the intense special interests of countless religious and political factions. And then, just as he reaches the secret at the heart of the confusion, people start shooting at him.

MacKinnon does such a good job of painting the murkiness of this world that the darkness and confusion obscure his plot, which is not, shall we say, easy to follow. In the end, Finding Hoseyn is better as a living portrait of the Middle East than it is as a novel.