Atomic warfare is unthinkable. Biological warfare is outlawed, messy and potentially dangerous to the aggressors as well as the victims. What to do next, in a world where the hardware of suspense fiction is constantly escalating? At the beginning of his third novel, Herbert Mitgang offers a new solution in soberly spectacular style: geological warfare. The Montauk Lighthouse, a landmark on the Atlantic coast for nearly two centuries, suddenly develops "a crack at the base of its red-and-white, candy-striped tower" and disintegrates under the force of a man-made (in fact, Russian-made) earthquake that sends shock waves running east into the ocean and south into the Pentagon.

In reaction to what the world sees as a natural calamity, American warships immediately begin patrolling the coastline -- not just the Atlantic, where it happened, but the whole continent; and the territorial limits are suddenly extended to 500 miles. Foreign shipping is rigorously kept outside that imaginary line, including the Soviet trawler Glinka, bristling with electronic equipment, which hovers eyeball-to-eyeball with the U.S. Navy.

For nearly a generation -- since the Bay of Pigs, let us say -- Americans who read the news thoughtfully have been wondering what super intelligence agency the CIA serves as cover and decoy. Herbert Mitgang states the point succinctly, through the voice of a Pentagon official, once the debris of the Montauk Lighthouse has been swept, temporarily, from his pages: "The CIA is not the big time! They're good for newspaper exposes and planted stories and books and winning Pulitzers for newspapermen who've been fed their line of crap by PR-types inside the company. . . I can tell you that they're small potatoes compared to us."

"Us" turns out to be not some deep secret but the old, familiar National Security Agency: "We have the real resources. We don't go around shooting off our mouths. But we owe the works -- the cryptology, the international monitoring of all the civilian and military messages and signals, the counterintelligence operations." What they don't have but acquire quickly to keep this quietly expert novel spinning to its ambiguous goal is Sam Linkum, "a man of middle years and middle accomplishments and burdens," who had previously been working for a newspaper that looks a lot like The New York Times (also Mitgang's employer). For reasons too complex to explain, Linkum is the logical man to deliver a very special message -- one sheet of paper containing a counter-threat -- from the Pentagon to Soviet intelligence.

While the Russians have been learning to cause earthquakes, it seems the Americans have been learning how to dry up large bodies of water almost instantaneously. This may sound even more fantastic than the earthquake weapon, but Mitgang makes it fairly credible (at least credible enough for this kind of novel) with a graphic description of a successful test in the United States and a Reuter's report describing the disappearance of Lake Ritsa in the Caucasian Riviera: "Yesterday the lake was there, and the same evening it disappeared off the face of the earth." The novel ends ambiguously, with no real assurance that a memo to the president from the Joint Chiefs sums up the possibilities: "The geological fault in the earth plates beneath the Montauk promontory was widened by remote control on command of the operational trawler Glinka . . . There are several thousand similar faults . . . subject to attack all over coastal United States. There are hundreds of large, vulnerable bodies of water . . . located inside the Soviet Union."

All this is handled readably, though Mitgang does send Linkum on a lot of trips -- to Sicily, Venice, East Berlin and finally Leningrad -- for rather dubious and unnecessary cloak-and-dagger work. Perhaps this is because he wants to describe the landscapes, particularly the art museums where Linkum usually makes his secret contacts. For readers who are not entralled with the action and suspense, an attraction of Mitgang's book may be its subplot. The paper for which Linkum works has been bought by a television network and is being transformed from an information medium to a sort of printed branch of show business.

Linkum quits the paper in protest, but gets inside reports from a colleague: "The paper's become mostly gossip columns in disguise and plugs for show business moguls and young executives on the corporate rise. . . Some new geniuses have moved over from the network to show us the light. And they've hired some new writers from the gossip-as-news magazines. Ambitious little who stand for not much of anything except their own careers."

This is, of course, an exaggeration, but it does represent a perceptible trend in print journalism -- one that may be a more clear and present danger to America than imaginary doomsday weapons. Television does not even have to buy a great newspaper to undermine journalistic standards; all it has to do is compete, at its chosen level, for advertising and audiences. One hopes and believes that the paper Mitgang serves as cultural correspondent is relatively immune to such pressures, but they certainly exist.