According to the AFI, Fox dropped the project when a disagreement on casting couldn’t be resolved. When Ladd left the studio to start The Ladd Company, Kasdan’s script languished at Fox. He presented his idea for Body Heat to Alan Ladd Jr., the head of 20th Century-Fox, who was interested in the project and put in on the books.
Kasdan took inspiration from his favorite filmmakers, John Sturges and Akira Kurosawa, as well as his favorite classic movies to update those styles of filmmaking with a fresh perspective. Lawrence Kasdan’s screenwriting career was on the rise thanks to his collaborations with George Lucas on two of the original Star Wars movies and Raiders of the Lost Ark (1981). Matty Walker, played by Kathleen Turner, is the object of his obsession and lures him into a plot to murder her investor husband Edmund (Richard Crenna). William Hurt plays Ned Racine, a sleazy lawyer whose lust for a married woman lands him in hot water. In Kasdan’s original screenplay, that premise takes on a whole new life with two new unsympathetic protagonists, a Florida setting and an unrelenting heatwave. The basic premise of a femme fatale and her lover plot to murder her wealthy husband was modelled from the noir Double Indemnity (1944).
Inspired by Kasdan’s love of film noir, specifically movies like The Big Sleep (1946), Out of the Past (1947) and The Asphalt Jungle (1950), Body Heat pays homage to the film noir style while boosting its sex appeal for a contemporary audience. By that time, it may be too late both for himself and for Matty.An atmospheric and steamy neo-noir, Body Heat (1981) is an impressive feature directorial debut by Lawrence Kasdan. But after he is unable to heed the advice of Peter and Oscar, Ned comes to some realizations about what he's gotten himself into. As they proceed with the plot, they encounter some unforeseen obstacles, including some the result of last minute changes to the plan by Matty without her notifying Ned beforehand. Since Matty signed a prenuptial agreement that would provide her nothing upon a divorce, they decide instead to murder Edmund. As their affair escalates into a declaration of love, it also turns to one of greed, wanting both each other and Edmund's money. She stipulates he can't tell anyone of their affair, which is against the general behavior of telling his friends, public attorney Peter Lowenstein and police detective Oscar Grace. Despite Matty playing hard to get, which turns Ned on more, the two begin a passionate affair. Ultimately she tells him that nothing will happen between them since she's married, her wealthy businessman husband, Edmund Walker, who comes to their home in upscale Pinehaven only on the weekends if that at all. She flirts with him despite his less than subtle come-ons and she thinking him simple minded. Although he spies several women as possible conquests, the one he really has his sights set on is the beautiful Matty Walker, who he can tell comes from money by her appearance.
The heat doesn't affect the overactive sex drive of womanizing Ned Racine, a somewhat inept Miranda Beach lawyer who has his own small law firm. A heat wave has settled over the Florida coast.