David Hare's "Knuckle" is cast in the form of a hard-bitten 1940s detective flick, with a hero who knocks back the booze, roughs up women, and carries at least two packets of fags, as they used to say, in his rumpled suit pocket. Name of Curly. Talks out of the side of his mouth. British arms salesman by trade. At the start of Hare's involving play, he's come home to England to investigate the disappearance of his sister on a remote beach called The Crumbles.

Foul play? Suicide? What?

Written in 1974, "Knuckle" is just now getting its area premiere at the Source Theatre, and while this production may test your patience during the first act, it's worth sticking with. In the second act, the threads of Hare's story suddenly entangle in bizarre knots and the Source cast, hitherto a bit uncertain, hits the proper tone. There's a kind of metallic flatness to it all--like looking at life reflected in the polished hood of an old Studebaker.

Curly's investigation takes him to a dive called The Shadow of the Moon, run by a sexy dame called Jenny, who wears belted coats and tosses her hair back, the way Veronica Lake used to do. It also leads him to the grounds of a hospital of sorts, where his sister, an idealistic type, worked as a nurse. He spends some time at the scene of the crime, cavorting on the ominous beach with Jenny. But as the clues pile up, he finds himself poking more and more around his father's palatial home. A successful merchant banker, that father. Lots of quiet decorum there. Something fishy.

The Source production, short on decor, uses slides to establish the various locales and movie music to underscore the action. But "Knuckle" is more than a theatrical retread of a film noir. Using an old form, Hare is exposing the climate of corruption and compromise that he sees as characteristic today of his native England. A society rife with deal-making, blackmail and greed. In this realm, bad deeds don't count--just bad publicity. "The horror of the world," says Curly, "is that there are no excuses left. Everyone knows the tricks."

And all the while we thought Curly was after a murderer. By the time Hare's play reaches its conclusion, a whole capitalistic way of life has been indicted. Curly's reaction? Well, it looks as if he just might pool forces with the corrupt. No heroes here. Heroes are for the movies, which brings us right back to Hare's starting point.

Source's production, directed by Stephen Hayes, makes a mistake, I think, by leaning too heavily on B-movie parody in the early stretches. (Jenny: "I was waiting for you to uncurl your lip." Curly: "That's how I keep it. Catches crumbs.") But mid-way through the evening, the direction and the acting deepen along with the story and you will find yourself drawn into a tantalizingly ambiguous world.

By then, Nick Olcott (Curly) and Veida Dehmlow (Jenny) have got the knack of Hare's hard-boiled repartee, which consists of delivering the crust but implying there's meat underneath. David Brown, as the victim's slimy lover, has found the shifty contours of his role. And Richard Mancini, as the father, comes quietly into his own, ironically just as he's trying to justify his shabby performance in the cutthroat world of commerce. As Hare puts it, "Humanity's a tough racket to be in."

Hare has written an interesting, shadowy play about a society that has replaced the old knuckle sandwich with corporate skullduggery. The real criminals, he's telling us, hide out in carpeted offices and do their dirty work with papers and bonds. Source's actors may seem to be outdistanced by it all at first. Nice thing is that they manage to catch up by the end. KNUCKLE. By David Hare. Directed by Stephen Hayes. Sets and lighting, Lawrence Redmond; costumes and props, Brigid McCormick, Amy Maness, Kathi Cochran. With Nick Olcott, Barry O'Rorke, Veida Dehmlow, Pauline Cottrell, Richard Mancini, David Brown. At the Source Theatre through April 30.