Meet La Femme Geena

RENNY HARLIN'S The Long Kiss Goodnight is the fall's best summer movie. Come to think of it, it has more pop in its popcorn than most of the actual summer movies this year--which is not, admittedly, saying a lot. A cheerfully preposterous cartoon that bounces energetically between carnage and comedy, it is smart enough never to ask the audience to take it seriously; Harlin simply serves up the nonstop twists and turns with such baldfaced enthusiasm you feel churlish pointing out that it doesn't make a lick of sense.

Would you believe this premise: a sweet schoolteacher with amnesia who slowly discovers that she was a gun-packing government assassin in her former life... who teams up with a low-rent private eye to figure out her true identity and finds herself the target of both her former nemesis, an international terrorist, and her ex-employer, the CIA--neither of whom is happy to see that she's still alive. It's ""La Femme Nikita'' meets Dr. Jekyll and Ms. Hyde, courtesy of a $4 million action-comix screenplay by Shane (""Lethal Weapon'') Black. Or call it ""Dye Hard,'' as the brunette model mom Samantha Caine, a smiling softie, transforms herself into the hard-bitten bottle-blond hit woman Charly Baltimore, both of whom come in the beguiling form of Geena Davis (Mrs. Renny Harlin), the liveliest and most convincing female action hero since Sigourney kicked alien butt.

Geena has the mouth you look at; Samuel L. Jackson, who plays the scummy but lovable gumshoe, has the mouth you listen to. He gets the best of Black's broad but fun- ny one-liners, and together they make a wonderfully improbable action team: she's the muscle, he's the reluctant brains. The movie even allows them a touch of erotic interplay--then drops it like a hot potato. Though some of the violence is nastier than it needs to be and the obligatory climactic melee, complete with choppers, skidding trucks and explosions, overstays its welcome, ""The Long Kiss Goodnight'' stays fun because it plays its heroine's split personality for laughs, not trauma. Charly creeps up on Samantha like an uninvited guest: here's the schoolmarm, innocently chopping carrots for her family's dinner, and suddenly she's wielding her knife with a furious precision worthy of Bruce Lee. The pride, befuddlement and wonder on Davis's face is delicious, as it slowly dawns on her--and us--that there's a beast inside this beauty. The premise may be a trick, but the movie's mostly a treat.