Canadians Pape and Aspler must figure that the idea of an independent Quebec is rivetingly nightmarish enough to support an international thriller of vast implausibility. It's doubtful, however, that many American readers will be all that riveted, especially since excess padding and a few too many red herrings insure a sluggish pace: plenty of time to notice the plot creaking and lurching along. Quebec's moderate Premier is assassinated--and the whole world quakes, waiting to see whether his successor will he another moderate or fanatic separatist Lacroix. And, as intrepid Montreal journalist Tony Redfern soon discovers, forces from all over are trying to influence the outcome: English industrial interests, the CIA (they attempt to kill Lacroix), and, above all, sneaky France--in the person of ""stunningly beautiful"" Monique, who inspired that initial assassination and is currently sabotaging the campaign of Lacroix's moderate opponent. Redfern, dodging both the CIA and the Royal Canadian Mounted Police, finally tracks down the evil Frenchies, but too late, too late, as Lacroix steams toward victory and the White House prepares to invade Quebec. . . . North of the border this may fan some anti-separatist flames; here the hottest news will be the incidental info that adulterous Montrealers slip away for sin to. . . Plattsburgh, N.Y.