PHILIP MARLOWE was always a hard one to figure. He was a loner, and he liked that way. A streak of cynicism ran through him as deep, his creator Raymond Chandler might say, as a spotted geister in a Chicago overcoat sent back-stroking in the blue Pacific. He was a hardened private dick, a real pro, and could trade quips and insults with any manner of wise-cracking low life. When a dumb and slutty millionaire's daughter tries to lead him on in The Big Sleep, cooing "you're cute," the unarousable Marlowe answers back, "What you see is nothing. I got a belly dancer on my right thigh." A real joker.

Yet Raymond Chandler's undauntable tough guy was a surprisingly soft touch when it came to certain ideals. Like professionalism: he prided himself on keeping his business on the up and up, on staying loyal to his clients, and on always sticking to his standard fee, $25 a day plus expenses--no more, no less. (That is, unless some old fogey with nothing better to do decided to get generous.) And he had a special prickly pride about his apartment at the Hobart Arms. The same tease mentioned above somehow manages to seduce a pass-key away from the super one night, comes in while Marlowe's gone and slips naked as Isis under his bedcovers. His reaction when he comes in says a lot about Marlowe. The woman offers herself up; he politely refuses. She flexes up on all fours and calls him by a filthy epithet. Then he tells the reader,

I didn't mind that. I didn't mind what she called me, what anybody called me. But this was the room I had to live in. It was all I had in the way of a home. In it was everything that was mine, that had any association for me, any past, anything that took the place of a family.

Marlowe had this kind of honorable soft center. But to get through to it, you still had a tough nut to crack.

All this comes by way of introduction to the character of Ira Welles, the aging, washed-up private eye that Art Carney plays in The Late Show. Welles isn't a total Marlowe facsimile, but he comes close. The circumstantial evidence is certainly there in the 25 bills Welles demands for fee and in the way he gets huffy when anyone suggests that he might be playing his game any way but straight. Even his affection for his sloppy $5-a-week room rings a bell; "it may not seem like much to you," he tells visitors in a defensive apology, "But it suits me fine." He's seen enough needless and sick crime in his 39 years in the business to become good and jaded. Yet like Marlowe, you never know when he's going to get his morality up.

There was one thing you could always say about Marlowe, though (as you could for all of the great city-wise private investigators in pre-World War II detective fiction): he was a man seeped in his surroundings. He knew all the personality types and all the hazy sights and smells of Los Angeles in the 1930s--right down to the bizarre styles of architecture and where you could find them. They were his life blood. If a guy came from the area, Marlowe could size him up and put him in his place in the time it took the man to flick the ash from his cigarette. Most of all, he liked the company of grifters--it never seemed to matter which side they were on. These types even had their own special language, and Marlowe was a professor of it. He never stopped being a loner, but it always helped to know that next day would bring another hood to trade insults with and another city cop to poke fun at.

TIMES HAVE CHANGED, however, and in The Late Show ulcer-ridden Ira Welles is having trouble learning to digest the new L.A. ambience. He's old, has a bad stomach and a game leg. Besides, no one hires private detectives anymore, unless it's for something screwy like finding a kidnapped cat. This is the first key angle in Robert Benton's script: the once respected and feared detective who's fallen on fallen times. Then there's the other angle: the funny lady who actually does ask him to sleuth down her cat. The woman, Margo Sperling, is played by Lily Tomlin. Her character comes straight out of a stock bit she does on television specials and in night-clubs: the astrology nut, pseudo-psychoanalyst and perpetual high-on-lifer all rolled into one. When Welles flashes a rod for the first time in her presence, she cheerfully informs him that "my shrink says that people who play with guns are usually impotent."

The two team up, and the case of the missing puss-puss predictably leads them into a tangled web of blackmail, murder and all the other sordid goings-on that the back of any good dime novel promises. This set-up isn't half bad, pairing a slowed-down gum shoe with a hanger-on from the age of Aquarius. As a mere thematic gimmick, however, it's not too much less than half bad, and risks making you wish that directors would cut out these nostalgic and unimaginative throw-backs to the classics. But extra dimensions fast begin to fill out thanks to Benton's cleverly constructed script and his skillful direction. Bit by bit, he manages to do about as fine a job of taking the pre-War detective format and creatively putting it in the 1970s as Robert Altman did in The Long Goodbye.

One way Benton shows that both the city and its underworld have changed is through the type of gangster he has Welles and Margo run up against. In the old days, the dangerous guys wore white pin stripes, ran gambling houses and could stay civil with private eyes because they invariably had the police in their pockets. (They said gentlemanly things like, "I'm nice to be nice to. I'm not nice not to be nice to.") In this new world the chief hood (played by a corpulent Eugene Roche) runs a hot vehicles and appliances operation--that is to say, he's a couple of legalities removed from a used car salesman. He has neither taste nor an eye for sharp clothes; his favorite seems to be a terry-cloth jumpsuit. And where the old racketeers had bodyguards with pug noses and club-steak ears, this fellow hires a turtleneck-wearing glamour boy (John Considine) who might just as well be Lyle Waggoner. What's more, these contemporary villains have lost all sense of decorum. They try to impress by breaking coke bottles across their mistresses' faces (the gangster in The Long Goodbye) or they think that to frisk an old man you have to work the ulceric guy over in the midriff and bloody his nose by grinding it into the wood paneling.

BENTON'S OTHER WAY of accentuating this juxtaposition of eras is through the unlikely combo itself: the old timer and the space cadet. This device is trickier, though; Altman and a lot of American film directors have tried the modern gangster idea and seen it work, while at first glance the oddball team device looks to be striclty situation comedy. Something That Girl would have larked into, or just the thing for The Sandy Duncan Show (a sitcom that keeled over in its break from the starting gate). And indeed, stereotyped situation comedy stuff it is.

But Carney and Tomlin elevate it. Carney may forever carry around like some prominent and embarassing tattoo his association with the hyper, dim-witted character of Ed in The Honeymooners. But here, like in Paul Mazursky's Harry and Tonto, he sheds that goofball image for a gritty grand-fatherliness. Tomlin is Tomlin, meanwhile: sensitive, talkative and--with all her blather about vibrations and kharmas--very, very funny. Yet what makes their two characters engaging and moving is the way they work together. If not a natural team, they both have become real pros and know how to make the audience believe in the kind of wacky bond that Tracy and Hepburn used to form.

There is also the matter of the plot, but you'll have to check that out for yourself. Let's just say that The Late Show has much of the style of some of the great Hollywood shamus movies. Benton borrows quite a bit, most notably a could-be corpse in the bathroom sequence from The Conversation and a manic chase scene from a long line of films. But he steals with style, and this movie has what these detective stories always required: laughs, suspense and the romantic angle. In this business these days, what looks like a bulging wad of potential often delivers about as much as a grifter's bill fold--an alluring top card that covers a bunch of hay. But in this one all the jake is up front.