Marilyn Sharp knows exactly what the furniture looks like in the rarefied reaches of the top floor at the State Department, and she can describe with total accuracy the layout of the presidential box in the Kennedy Center Opera House. She seems to be not a technician herself but willing to consult in detail with technicians who can tell her about state-of-the-art techniques for scrambling and unscrambling a top-secret tape recording. She appears reluctant to kill people, which might be considered a weakness in a writer of suspense fiction, but when the occasion demands a colorful death she will grit her teeth and produce it as required. And she will make it believable -- perhaps precisely because she approaches literary bloodshed as a demanding part of her craft rather than an enjoyable hobby.

In her second novel, "Masterstroke" (the first was "Sunflower"), Sharp has an incredible tale to tell, and her command of realistic detail in such peripheral matters as furniture, technology and modes of assassination aids considerably in making it more credible. It is also a complicated tale -- perhaps a twist or two more complicated than is necessary -- but on the whole she makes it reasonably lucid. She is not one of the supreme prose stylists of our time, but she uses words efficiently and effectively.

The story focuses on an American-Soviet conference, scheduled to be held on the Yuglslav island of Korcula, which the U.S. president and the Soviet premier have pre-engineered to become a breakthrough in international relations. At the climax of the Korcula conference, a treaty is to be signed that will establish firm international standards of respect for human rights, and as a spectacular initial gesture of compliance, the Soviet Union will announce a massive release of political prisoners, including the Soviet Six, a group of dissidents who have become an international cause celebre: "a diverse group, ranging in age from twenty-four to seventy-one. A scientist, a novelist, a professor of economics at the University of Moscow. A physician, a university student, a young composer and pianist. Among them a Nobel Prize winner, a Lenin Scholar, a Tchaikovsky medalist, and a Hero of the Soviet Union. . . . They had all requested permission to emigrate to Israel, and now they were all life inmates of the labor camp called Perm."

There are people, perhaps on both sides of the Iron Curtain, who do not want the Korcula Conference to work, and they have set complex machinations at work to scuttle it. The Soviet Six are mysteriously allowed to escape from Perm (perhaps with help from the CIA) and are set on six separate paths out of the Soviet Union. One of them is carrying a tape with potentially explosive contents -- but nobody knows who has the tape, not even the escapees, five of whom have tapes identical with the real one except that they are blank. As for what is on the tape, that is a mystery that can be unraveled only with special, computerized equipment and a counterpart tape, also top secret, that is concealed in the home of U.S. Secretary of State Arthur Compton.

The mysterious forces working against Korcula converge for obscure reasons on Peter Lucas, as assistant to Compton who is also in love with his daughter, Nicole. While the escapees are being picked off one by one in the Soviet Union (thus depriving the conference of its climax before it even convenesd), Peter is being subtly pushed toward curiosity about their fate, about the mysterious tapes, and about the dark underside of Korcula, which may be revealed if the tapes can be decoded. Can it be that the United States is making unacceptable concessions in return for the Soviet gesture? Can it be that those concessions are recorded on the tapes? It sure can, but you will have to read through 300 pages of twisting plot before reaching with such answer.

From the evidence in "Masterstroke," Marilyn Sharp seems to be a writer oriented toward mystery fiction (which is not currently magic at the cash register) who has more or less successfully shifted herself into the mode of action-suspense fiction (which is). She pushes a simple-minded genre to the limits of both complexity and credibility, with her intricate plotting and some bizarre episodes. A key plot element, for example, happens on a single night in Washington: the violent deaths of two men, a Yugoslav diplomat and a human-rights activist, who both die muttering cryptic sentences which turn out, eventually, to have a bearing on Korcula. The process by which Peter unravels these mutterings is a Philo Vance or Sherlock Holmes procedure, not the kind of thing James Bond would do, and Peter's life is not in real danger at any point in the plot, as the lives of action-suspense heroes have to be by unwritten law.

But suspense is, or should be, a wide-ranging, inclusive kind of writing, and if Sharp stretches its boundaries a bit, she hardly inflicts lasting damage on it. Even when her plot goes into baroque over-elaboration, it is calculated to keep the pages turning complusively, and that is what this kind of writing is all about.