ERIC OVERMYER'S new musical detective spoof "In a Pig's Valise" gleefully nicks from such film noir flicks as "The Maltese Falcon" and "Chinatown," borrows hardboiled B-movie lingo from the likes of Chandler and Hammett, and piles on the genre cliches: choking clouds of dry-ice fog, voice-overs, flashbacks and lots of sax and violence.

The first of three new plays in rotating repertory at Center Stage's "Playwrights '86" series in Baltimore, "Valise" gets a polished premiere production, but the play itself is obviously unfinished. With some loose threads snipped and some shrinking and expanding in the right places, "Valise" could become a camp cult musical along the lines of "Little Shop of Horrors."

Lurking in the plentiful shadows of the seedy Heartbreak Hotel (at the corner of Neon and Lonely streets, natch) are familiar demimonde denizens: self-doubting shamus James Taxi (whose habitual monologues drive the other characters nuts); endangered dame Dolores Con Leche; the villainous brothers Bucket (Shrimp and Gut); and a handful of henchpeople with names like Zoot Alors and Mustang Sally.

Overmeyer is far more concerned with wordplay than gunplay, and lets the preposterous plot, involving the theft of dreams from ethnic dancer Dolores, get away from him. The playwright has great fun slinging the slang, slathering the script with wincingly bad puns and sophomorically salacious jokes. By act two, however, most of the humor has been wrung from the detective device, and as Overmyer starts straining for puns and a plot, "Valise" starts slowly falling apart.

Songs like "Kiss Me Deadly" and "Echelon of Scum" don't move the plot much and remain clever rhymes in search of a tune, but the atmospheric accompaniment, composed and conducted by Washingtonian Karl Lundeberg, is reminiscent of Steely Dan's smoky, shimmering electronic jazz-pop.

The Center Stage cast (and the audience) still seem unsure of where the laughs are, but laudable performances are given by Jack Kenny as affably laughable gumshoe James Taxi, and Yamil Borges, who plays Dolores Con Leche as the most fatale of femmes, with a beestung pout and arched eyebrows lifted from Faye Dunaway.

Hugh Landwehr designed the set, several towers that revolve and recombine to create locales in and out of the seedy Heartbreak Hotel; lighting designer Pat Collins conjures deep, dark shadows in a murky blue and green neon night.