"Impulse," the new Sondra Locke film starring Theresa Russell, ricochets from the cliche to the improbable. Set in Los Angeles, the picture is about Lottie (Russell), a foxy blond narcotics cop who pulls a second shift nights as an undercover vice cop.

So you know it's got to be good.

Predictably, what this involves is a lot of screen time devoted to Russell, who's amply equipped for the duty, parading around in skyscraper heels and a Saran-Wrapped, leopard-skin mini, luring johns and crack heads to their doom. Thing is, she likes it, likes the butch thrills and the power games, and even fantasizes to the shrink who's been assigned to evaluate her suitability for the job that she longs to cross the line and actually take the money, experience what it's like to lose control.

So what does the shrink do? Puts her right back out on the street.

Along the way, Lottie becomes romantically involved with assistant district attorney Harris (Jeff Fahey), who drags her into a case against a powerful drug lord. His big mistake is that he's nice to her, causing her to flee, quite accidentally and quite miraculously, into the arms of the kingpin, who's murdered while she's in his apartment, leaving her with the corpse and an attache case containing $900,000.

Aside from the overwhelming fact that there cannot possibly be anything else we want to know about the inner machinery of an undercover cop, male or female, "Impulse" makes it absolutely impossible to think and enjoy ourselves at the same time. Forget that Locke actually manages to approach the emotional scenes with some originality, and that as an action director she's no worse than most of the journeymen filmmakers in Hollywood. The movie insists on our being mindlessly accepting, and her grace notes aren't allowed to register. It gives us no choice but to get dumb.