Cataclysm by William Clark (St. Martin’s: $15.95; 312 pp.)

“Cataclysm” offers a lightly novelized scenario in which an international debt crisis escalates into all-out conflict between the developed and underdeveloped worlds--called North and South by novelist William Clark.

International debt is something Clark should understand after 12 years as a vice president of the World Bank. His inside knowledge is obviously intended to make “Cataclysm” plausible and therefore compelling--so much so that style and characterization complaints are almost beside the point.

The cataclysm begins at an International Monetary Fund meeting in 1987. Mexico proposes a freeze on loan repayment by the debt-laden South. Led by Britain and the United States, the North does not try to negotiate a compromise. Instead it takes a hard line inconsistent with the IMF precedent of trying to avoid debtor nation default at any cost--though stupidity is always a factor in world politics.

The South defaults on its loans. The North expels most debtor nations from the IMF and stops transfers of funds. The South begins to starve and decides to fight back. Clark intercuts the action with observations on debt: “Since they (the North) had lent far more money than the total of their equity and reserves, they were in effect lending borrowed money.”

“Cataclysm” is flatly narrated--as opposed to dramatized--perhaps to evoke a hastily compiled paperback history in which nations, not individuals, are the real protagonists. Lone phrases of dialogue drift in paragraphs of AP wire copy prose: “ ‘This is so much less trouble and more intimate than going down into the Situation Room,’ the President murmured.” Other principals--the president of Mexico, the U.S. secretary of the treasury--get an adjective apiece to flesh out their characters and then unload longish monologues.

The quirks of international finance can be interesting--in the year since “Cataclysm” appeared in Britain the United States has become a debtor nation for the first time in 75 years. But Clark moves away from his insider’s view of world debt to become more speculative--and less plausible.

Would Chile and Argentina really turn their economies around quickly and completely if relieved of debts? Would South Africa fall so fast and totally to black guerrillas? When the South knocks out the North via disruption of its electronics and computers--a sabotaged satellite causes an irreversible Wall Street crash and depression--Clark cites the movie “WarGames” as proof it can be done.

Clark, a Briton, primly assures us that the South’s terrorism is not nasty like that of the IRA. The South’s leaders are wise and kindly in humbling the North--presumably Rambo was somehow unavailable to the United States. We finally suspect “Cataclysm” is not a scenario that Clark finds plausible so much as one he would like to occur--a suspicion strengthened when the beaten North joins the South in new, improved IMF. “Cataclysm” seems in the end World Banker Clark’s daydream, as if a dentist were to publish a novel about how the world is saved by someone who cleans teeth.