Another Forsyth countdown thriller--this time in 1987 Britain, where (in the novel's last 150 pages) the men of MI5 will be madly scrambling in order to prevent a USSR-engineered nuclear ""accident."" Before the countdown begins, however, Forsyth teasingly moves back and forth between two slowly-developing plots, which will link up only in the novel's final moments. Plot #1: British Intelligence accidentally learns (thanks to the patriotism of a top jewel-thief) that there's a leak high up in the Defense Ministry; John Preston of MI5 eventually traces this leak to right-winger George Berenson, who thinks he's been slipping secrets to South Africa. . . but has really been slipping them to a Soviet mole within South Africa's diplomatic corps! (Preston's sleuthing takes him to South Africa, and back into WW II archives.) More central, however, is Plot #2: in Moscow aged Kim Philby (a nice cameo) is helping the USSR General Secretary to formulate ""Plan Aurora""--whereby a nuclear accident in England will swing the upcoming general election over to the Labour Party (which now belongs to the ""Hard Left""), ushering in a Marxist-Leninist ""British Revolution,"" not to mention the end of NATO. And Plan Aurora involves the infiltration of a dozen or so Soviet (non-KGB) agents into England, each one carrying some ingredient for Moscow's violation of the ""Fourth Protocol."" (One of the secret clauses in the 1968 Nuclear Non-Proliferation Treaty, this Protocol bans the hostile use of miniature, smuggled-in nuclear weapons.) Preston of MI5 begins to suspect what Moscow is up to when one of the Soviet couriers is accidentally apprehended in Scotland, carrying ""a disk of pure polonium""--which, when placed next to a disk of lithium, becomes a nuclear-bomb ""initiator."" A search for other Soviet infiltrators begins, eventually focusing (with SAS support) on the key bomb-man, an English-speaking mole. But, though Preston & Co. are super-efficient, successfully closing in on the villains before the explosion, it's eventually revealed that the English were being aided all along by certain forces within Russia--a development which links up (too predictably, too late) with that other, Defense Ministry-leak subplot. This not-quite-satisfactory interplay between the plot-pieces is only one weakness of Forsyth's new thriller: the characters are all rather flat; the countdown lacks Jackal-level tension;the political material (Labour Party background, etc.) is ladled on with a heavy hand. No matter. With his no-nonsense style and shrewd sense of variety and pacing, Forsyth remains a superior (if unoriginal and unmesmerizing) entertainer--and this lesser effort is sure to grab the same no-frills readership (not a speck of romance or sex here) that has made him a top-seller again and again.