A thriller so lightweight its characters should be required to carry change in their pockets to keep from blowing away.

That's the single-"Jeopardy" answer to the following question: "What is 'Double Jeopardy'?"

Beginning with an intriguing premise, which it manages to squander in record time, it turns out to be a thinly imagined, thinly acted, silly exercise in car crashes, chases and nasty outbursts of generic violence that leave you with the following answer: bother.

The question: Why did they . . . ?

Ashley Judd, who may be a good actress if she ever gets out of B-level films like this one and her previous and undistinguished "Kiss the Girls," plays Libby Parsons, a young wife and mother who apparently has it all: Coastal mansion in Seattle, beautiful son, handsome, successful husband Nick (Bruce Greenwood, probably the best one in the cast) and a life of utter stability and prosperity. One weekend, however, her husband takes her sailing; she wakes up in the middle of the night to find him missing and his blood all over the boat. So just like a stupid character in a bad movie, she picks up the bloody knife a second before the Coast Guard shines its everlasting light on her.

She's swiftly (and unconvincingly) convicted of murder. Her son, adopted by a friendly (and beautiful) teacher, disappears. In prison she tracks the disappeared woman over the phone, and learns, all too conveniently, that Nick still lives. He's framed her, taken their son and his insurance payout and is living large with the teacher.

Six wrinkleless, ungrayed years later, she's paroled in the gruff care of her probation officer Travis Lehman (Tommy Lee Jones); she flees from the halfway house at the first chance she gets.

That's the first 45 minutes, but it plays like 10 minutes; for the next 60 minutes or so she tracks down her hubby, while herself being pursued by the ever-dogged Jones. You can see two templates underneath, struggling for supremacy but ultimately canceling each other out. The famous one--Jones's pedigree guarantees the connection--is to "The Fugitive," that classic of the double pursuit, the same blueprint as here. The other is the less-well-remembered Tom Selleck thriller, "An Innocent Man."

The ads and trailers suggest the latter is more important--as in Selleck's film, Judd is an innocent in prison, where, in theory, she learns the skills and strengths of a criminal and comes out hardened and equal to the task of achieving justice. Well, sort of. Actually the film throws this interesting theme away for a few silly scenes of her jogging or weightlifting in the rain.

She does encounter the movie's most intriguing possibility, however--again, something played up in the ads. Since she's served her sentence for murder, she can kill Nick, apparently without legal penalty. (Why do I doubt this is true?) Again, the movie walks away from this after evoking it, never exploiting it for maximum irony or surprising twists.

In fact, "Double Jeopardy" really just unfolds without much thought or planning. It's 100 percent twist free. Bruce Beresford, the great Australian director fallen upon mediocrity in his American phase, just seems to want to get it over with. The script never provides Judd with a plan; she just improvises frantically, coming up with solutions that frequently require her to break the law and wreck property. Beresford tosses in a few big action set pieces--Judd and Jones are trapped in a sinking car after her escape attempt, she bulldozes her way out of a town with her truck and she's trapped in a coffin with a dead guy--purely as emulsifiers to jack up the thickness of the plot, but all three are basically irrelevant to the story. There's not a single clever stroke or reversal in the film--the ads have given away Nick's survival--and the whole thing ends in a simple fight in an office.

Meanwhile, Lehman's pursuit is but a minor note in the film, even as he's beginning to believe in her. He never becomes the commanding figure that made him a star, just a sort of rumpled civil servant with an attitude problem. There's not a single moment as electric in the film as the great one in "The Fugitive" where Harrison Ford says to Jones, "I'm innocent," and he replies, "I don't care."

"Double Jeopardy" is guilty. I don't care.

Double Jeopardy (106 minutes, at area theaters) is rated R for violence and profanity.

CAPTION: Ashley Judd and Tommy Lee Jones in the all-wet "Double Jeopardy."