A PERFECT WORLD, with Kevin Costner, Clint Eastwood, Laura Dern, and T. J. Lowther. Directed by Clint Eastwood. Category II. At the Palace. THE landscape of the Texas panhandle across which Clint Eastwood's lawman pursues Kevin Costner's fugitive desperado is, we are told, a labyrinth of roads going nowhere - of highways turning into by-ways turning into dirt track dead-ends. The same can be said of the film itself. Just about all of the secondary characters here (including that played by the director) prove to be pointless diversions to the only broad, straight road that actually leads us anywhere - the one driven by Costner's Butch Haynes. At least the red herrings are conveniently packed together in their own little tin can - a gleaming hi-tech trailer, commandeered to serve as a mobile HQ for the posse, and to supply some rather unnecessary light relief. There is Red ''The Herring'' Garnett (Eastwood) - red indeed, in face and neck - the revered Texas ranger who, it turns out, had inadvertently set Butch on his road to ruin some years back; Laura Dern's hyper-intelligent, utterly decorative criminologistSally Gerber; a nice fat sheriff who is there to tell us what a great guy Red is; and a standard issue black-suited, dark-shaded federal agent who actually does play a role in the end, but is not written up nearly far enough to do the job properly. Meanwhile, back in the mainstream, Costner is really in the driving seat and getting all the mileage out of his best-written role since Bull Durham (the two-dimensional hero of Dances With Wolves notwithstanding). It is a great reading of a dream role for an actor of Costner's type - a charismatic, chivalrous, morally ambivalent, free-spirited yet psychotic outlaw who was raised fatherless in a New Orleans brothel where he killed his first man at the age of eight - but who might just be a good man looking for redemption despite it all. ''A criminal's criminal,'' the decorative Dern notes. Along for the ride, as a kind of emotional navigator, is a young lad named Philip (Lowther). He is eight years old, fatherless and was raised as a Jehovah's Witness (note subtle variations in the two resumes). Philip is kidnapped as a hostage by Butch and his no-good, child-abusing partner after they break out of jail. If there is one thing Butch can not abide, though, it is a child abuser - so the partner gets popped pronto. And Butch and the boy head out on the open road in a series of stolen cars. It does not take a genius to predict the nature of the bonding process that develops between the two, and very pleasurable it is too, thanks to good dialogue - even if the junior partner lacks the sure command of buddy-buddy banter of, say, a Susan Sarandon or a Geena Davis - and Eastwood's deft direction. The big man's real talents in that department, though, have always lain on the dark side and it is not until things take a shockingly sinister turn that his films are ever really touched with brilliance. But where does all this leave the much-vaunted Clint-meets-the Fugitive premise? Answer: two hours down the line, somewhere out in a field in the middle of Texas. Like so much in A Perfect World - like the setting in 1963, in Dallas, just before JFK's fateful visit - the promise builds preconception but never pays off. It is just another red herring. A Perfect World is a film starring Kevin Costner, directed by Clint Eastwood - and that is about as close as these two saviours of the western genre get in this semi-contemporary western manhunt. For Eastwood, of course, it is another return to familiar territory. Every Which Way But Loose it is not - but we do get dumb-ass hicksville sheriffs, accommodating roadhouse waitresses, and big automobiles by the busload, even a cross-country car chase. If Eastwood had only taken a firmer hold on his sub-plots, he might have made the best road movie with a message since Thelma and Louise. As it is, A Perfect World scores a less than perfect six out of 10.