A Chase Thriller Running on All Cylinders : DADDY <i> by Loup Durand (Villard Books: $18.95; 377 pp.) </i>

“To write a thriller,” the late John Braine once proposed, “you begin with improbability. . . . The hero must always be in danger. He must at least once be helpless in the hands of the enemy, and he must escape.”

Loup Durand follows this formula slavishly. “Daddy,” a major best seller in France and throughout Europe, not only begins with improbability but remains consistently improbable, even absurd, throughout. In doing so, it makes one consider the entire question of genre writing. For one would expect that any book so formulaic would lie there lifeless, inert, at best a book you keep reading for its plot while you berate yourself for surrendering to such obvious claptrap.

Instead, this book is alive and vibrant, compelling in its suspense, rich in character and incident. Set in Europe during World War II, the story is put into motion when an elderly banker, who has funneled hundreds of millions of dollars out of Germany for Jews and others, is caught and tortured by the Nazis. He leaps from a window to his death before he discloses the immensely complex series of secret access codes, which alone would allow the Nazis to reach those funds. Only his granddaughter, Maria, knows the codes, and she has taught them to her only son, the genius Thomas, who holds them all in his head.

The Nazis want that information and set up a fiendishly effective team to track it down. Essentially, the book is a manhunt, although the “men” being hunted are, first the lovely Maria who has lived a remarkably independent life and who is loved and protected by many people, most notably a team of preternaturally capable Spanish bodyguards; and later her son, Thomas, an 11-year-old boy of inhuman intelligence and perspicacity and yet--in perhaps the major victory for Durand’s writing skill--immensely likable. If we did not care for this boy Thomas, if we did not ache for him when he watches his mother die in flames, if we did not feel his unwillingness to attach himself to others when he has seen so many who’ve been kind to him killed, if we did not feel his darknesses and his hatreds and his fears, there would be no book.

Obviously, we have to suspend disbelief here. This boy with his “rat’s instinct,” his “frightening abnormal lucidity,” has the ability to outthink, outplan, outfox, an immensely resourceful adversary, the epicene Nazi genius Laemmle whose obsession with the boy becomes pathological. They play chess against each other, real chess when Thomas is Laemmle’s captive, figurative chess across the map of Europe when he is on the run. Chess becomes a leitmotiv throughout the story.

Much the weakest element in the book is the man who turns out to be Thomas’ real father, a playboy Rockefeller-type from America, who has never known of Thomas’ existence. David Quartermain is totally apolitical, a man of no commitments, completely uninterested in the family international banking business (which turns out to have continuing important connections with Nazi Germany throughout the war). Ultimately, David responds to Maria’s summoning him to Europe and becomes Dick Daring, performing astonishing feats of bravery, skill and planning. It’s as difficult to believe most of this as it is to accept that a man of obvious intelligence and wealth in 1942 would not know why France was bisected into occupied and Vichy-controlled sectors, or what a “Petainist” was. Quartermain seems almost a Frenchman’s view of the noble savage, ignorant but instinctively in touch with the good and the true.

The great success of “Daddy” is in Durand’s teeming imagination. An abundance of plot, of imagination, of incident, lends a richness to the book’s texture--no minimalism here--yet never buries the main narrative thrust--the chase. Along the road of life, we meet dozens of characters who are individually delineated--Nazis brutal and cynical, brilliant and dense, French chevaliers and graspers, ordinary people fearful or singularly brave, (although there certainly seem to be more Resistance heroes per hectare than history, as Marcel Ophuls has pitilessly revealed it, really produced). This is not genre fiction as high art, in the Le Carre mode, but it is commercial fiction of great skill and energy.

A word about the translation from the French by J. Maxwell Brownjohn: It is seamless and idiomatic, without a single clumsy construction. It’s a remarkable achievement to sustain a breakneck narrative pace and never once sound as if the book was written in anything other than English.