Were the guns still smoking from the Six Day War while Morris West was translating the event into The Tower of Babel? If so, then he might well have written Harlequin while waiting on the gas line, incorporating as it does last winter's oil crisis into an international political thriller. The story is narrated by Paul Desmond, an Australian, well-to-do, middle-aged, cosmopolite, ambassador-at-large for Harlequin et Cie, an old line Swiss-based merchant banking firm presided over by a paragon of accomplishments, George Harlequin. Harlequin has coasted his way through the world of finance by virtue of his privileged background, charm and a certain disdain for the grubbier aspects of his line of work. Until his bank is discovered to be fifteen million dollars short. Then he must descend to the arena to fight it out with Basil Yanko, American manipulator and mastermind in charge of Creative Systems whose interests form a global network of conspiracy and assassinations. During the course of their conflict--which takes place in New York, Washington, London, Mexico City--Harlequin's wife is murdered, his son is kidnapped and he himself is altered into a kind of white hat Yanko--a ""villain by necessity,"" as West quotes King Lear. Eventually Yanko caves in but however conveniently the actual coup de grace is delivered by one Aaron Bogdanovich, Israeli terrorist who has none of the qualms which beset West's heroes. Judging by this effort and its predecessor, The Salamander, West is now cruising at a lower altitude. The result is less pretentious, more likable and more satisfying.