BODY HEAT -- At the AMC Carrollton, Avalon, K-B Cerberus, K-B Cinema 7, K-B Langley, NTI Tysons Center, Showcase Bradlick and Showcase Pike.

"Body Heat" is a story for a hot and steamy night. The beercans sweat. The iced tea sweats. The world swelters in the sultry miasma of a night of the iguana, and Ned Racine (William Hurt) glistens in the moonlight. It is, as his police detective friend observes, the kind of heatwave where "pretty soon people will start thinking the old rules aren't in effect."

It's the story of a murder and a puzzle that leaves one feeling unsatisfied. Ned meets Many (Kathleen Turner in her debut) and Manny (Kathleen Turner in her debut) and is irresisbly drawn to her. In a moment of sarcasm that stands out in the otherwise banal dialogue, Manny quips to Ned, "You're not too smart, are you? I like that in a man." It's a prophetic remark: Ned's stupidity is his fatal flaw.

Finally, when the sound of her wind chime collection drives him mad with passion, he grabs a porch chair and crashes through a glass door into her waiting arms. Faced with the inconvenience of her marriage, he follows his hormones wherever they lead, and the couple plots to do away with her husband (Richard Crenna).

Now if this sounds a bit like "The Postman Always Rings Twice," that's because it is very much like it, from the murder down to mutual betrayal in the aftermath -- even down to the wife's wearing short shorts. ("Body Heat" was written by Lawrence Kasdan, who also wrote the screenplay for "Raiders of the Lost Ark" from a George Lucas story.) Early on, with much writhing of bodies, the plot is pretty slow going. But in the last half-hour, those who still believe that love conquers all are in for some surprises as the plot resolves itself with a new twist on the "Postman."

However, when the movie is over, the puzzle is still missing a piece: how could a sympathetic character like the lawyer played by the boyish William Hurt -- who shivers as he hears the jailhouse door slam between himself and his criminal client -- decide to hurt anyone? It's either a terrible case of miscasting, or the screenplay left something out in character development: There's no insight as to how Ned changed from over to killer. Bumping off the old man, he tells Manny, is "the only way we can have everything we want." Right, he wants her and she wants money. Divorce would have been much simpler, but she stands to inherit half her husband's fortune. In fact, she tells Ned, she wants all of her husband's estate. "We can't get greedy," Ned admonishes.

In the second half of the movie, Ned looks continually befuddled -- as if the transition bewilders him, too.