Something Fishy in Siberia : POLAR STAR <i> by Martin Cruz Smith (Random House: $19.95; 373 pp.) </i>

Eight years after “Gorky Park,” his densely atmospheric and best-selling detective thriller about a triple murder in Moscow, Martin Cruz Smith looks in again on the career of Arkady Renko, the MVD homicide investigator who worked the case.

The career, frankly, could not be in worse shape. Disgraced for breaking a whole book’s worth of rules during the investigation (the murders had international political overtones), Renko was sent to a psychiatric hospital to have his mental attitude adjusted. He escaped to the mindless rigors of a Siberian work camp.

He fled again, pursuing what seemed a soul-eroding downward spiral, and in “Polar Star,” is working on the “slime line,” the fish-gutting stage aboard a huge Soviet floating fish factory in the Bering Straits. It is a U.S.-Soviet co-venture, with the “Polar Star” processing the catch from American trawlers.

Renko, whose identity is not a secret to the ship’s officers and whose reputation for political unreliability has arrived with him, cannot leave the ship even on its infrequent dockings at fun spots like Dutch Harbor.

When a sexually active female worker (the factory ship is co-educational) turns up, against all likelihood, in one of the trawler nets, it is murder, despite a suicide note that is conveniently found, well after the fact. Renko is returned to duty as an investigator (amid extreme reluctance, on his part and everybody else’s). His job, it is made clear, is to prove that it wasn’t murder.

Smith, who reportedly talked his way onto one of the actual Soviet factory ships in guise of a magazine journalist and stayed until a Newsweek story on “Gorky Park” blew his cover, reports the shape, size, smells, work routines (alternately dangerous and depressing), off-hours life-style and weather conditions (invariably foul) of the Polar Star and its accompanying trawlers in endless and engrossing detail.

Like first-rate fiction in any genre, Smith and “Polar Star” take the reader deep into unfamiliar territory, and the journey has the excitement of fine reportage.

But Smith is also very good indeed at inventing what goes on in this exotic environment. Renko has a terrible time. He is lied to (of course) at every level. He is slugged and left to die in one of the quick-freeze lockers--a stunning narrative sequence. There are chases aboard and ashore. (He is able to be smuggled ashore at Dutch Harbor, where the plot thickens further.) There are hair’s-breadth escapes from fire and knife and a climactic confrontation on treacherous ice. Of comfort no man speak.

With all the action, Smith is also, as he was in “Gorky Park,” fascinated by the dynamics of Soviet society: the edgy relationships within it and the mental states of a man like Renko, who does his unsuccessful best to appear gray in a gray society but who is by nature a kind of pre- glasnost maverick, likely to find the hot water in any society.

One crime fiction anthology said of “Gorky Park” that along with its excellences of style and plot came a pervasive air of “dismal hopelessness.”

Renko’s pursuit of the murder, despite all the unofficial and official obstacles put in his way, leads him to a ring of smugglers. The smuggling is not really big-time stuff, but it eloquently suggests a deep thirst for capitalist fancy-goods. He discovers evidence as well of distrustful espionage by both the Soviets and the Americans (a nicely satiric commentary on the paranoia that glasnost and perestroika have not significantly eradicated).

The dismal hopelessness has not been eradicated either. Life along the slime line appears almost as dismal as hopelessness ever gets. Flashing back on his escape from Moscow to Siberia, managed with the help of friends, Renko muses: “It was as if everyone traveled the world in the dark, never knowing where he was going, blindly following a road that twisted, rose and fell. The hand that pushed you down one day helped you up the next.”

There is at least a glimmer of hope in such a musing--light along the tunnel if not yet visible at the end of it. And the hope has a sardonic tinge. A friend who is helping him escape to Siberia explains why Renko will be safe there: “They say some waters are too cold even for sharks.”

The writing in thrillers is frequently of serviceable but not distinguished or exhilarating prose. Ludlum and Forsyth are read for their action and their complex and occasionally ingenious plottings. John le Carre, second to no one as an inventor of convoluted plots, is perhaps most enjoyed as a prose stylist capturing mental and emotional states of marvelous subtlety.

Smith is not quite in Le Carre’s class. But, as when he is evoking the austere seascapes of this remote geography, he achieves a kind of prose poetry. “Gulls burst over the Polar Star as if blown by light that rolled like a wind over the factory ship. Clouds lit. The windows of the trawlers flashed, and at last, out of the dark rose the low, green shore of home.”

“Polar Star” joins the still-narrow shelf of novels of crime that transcend the form and, in the name of entertainment, illuminate their time.