"Hello Mary Lou: Prom Night II" may be derivative, but for the most part it's clever enough to trade on its sources with humor and class. It's "Peggy Sue Lives on Elm Street," with dollops of "Carrie," "The Exorcist" and a half dozen other genre stalwarts.

Seems that back in 1957, brand-new prom queen Mary Lou (Lisa Schrage) gets burned up on her special night after a jilted boyfriend accidentally sets her dress on fire. Of course ignition seemed inevitable after the scene in which Mary Lou goes to church to make a long confession and ends up leaving a "for a good time" number written on the wall in bright red lipstick.

Flash forward 30 years. The jilted boyfriend (Michael Ironside) is now the high school's principal and his son (Justin Louis) has a crush on a nice girl (Wendy Lyon) who wants to be prom queen despite the opposition of her fundamentalist mother. Denied money for a dress, she sneaks into the school theater department's prop room and finds a musty old trunk. Guess whose wrap, tiara and unruly spirits are let loose when she opens that trunk?

Lyon (who looks as though she's awaiting a 10th reunion, not a graduation) and Louis are nice kids, but so are their friends who soon start getting killed off, an unusual twist. Lyon, who alternates between being remarkably self-possessed and just plain possessed, has great fun when Mary Lou takes over, slipping into what one pal calls "a fashion coma" and sounding as if she's just stepped out of an early Elvis Presley movie. As she wreaks her vengeance, she's also remarkably flip. At one point she leaves a telephone message saying, "I've got places to go, people to kill," which is exactly what she does.

Unfortunately, Ron Oliver's screenplay fizzles at the end with a "Carrie-ish" rip-off and he can't resist the obligatory closing shot that's supposed to be a final shock but quickly becomes de rigueur mortis. Director Bruce Pitman keeps things moving and offers some actual exposition (now that's a shock). The special effects are more implied than drawn out, suggesting that "Hello Mary Lou" is a step back from the gory-telling that's come to dominate the genre in recent years. Hello Mary Lou: Prom Night II,

Now playing at area theaters, is rated R and contains scenes of violence and some nudity.