ONE MAD, IMPETUOUS dawn with Sam Neill and Meryl Streep is never the same again. For 20 years, she cherishes their night of passion in war-torn France, never again taking off her clothes to have sex.

Streep is lovely, accomplished, meltingly sensual, photogenic, a pleasure to behold in her new movie "Plenty." But it never starts anywhere and never goes anywhere. It's a hurky-jerky biography of a diplomat's wife who hates her comfortable post-war life. She likes losing control and eventually cracks up.

Neill plays the one-night stand who haunts her, a memory of her idealistic youth. And Charles Dance (called the thinking woman's crumpet in some circles) is her sweet- natured if overly supportive husband. He ought to get her mind off Sam, but he's too stuffy -- just like the movie.

Not even Sting, whom she regards as little more than a sperm donor, can distract her for more than a moment when the two wriggle contentedly on a couch at the queen's coronation. Streep wears a lovely purple dress, but does remove a matching hat for the occasion, and I don't mean the coronation.

British playwright David Hare, who adapted his prize-winning play for the screen, botches the translation with the help of Australian director Fred Schepisi. The nonchronological play becomes an overblown, visually complicated screenplay. And like Hare's recent film "Wetherby," it's doggedly slow and virtually without transitions.

The dialogue sounds like pornography written by Victorians, fruity and overblown. The heroine worries, for instance, that her boss will rub his body on her ledgers, that he will take her "ears and rub them on his thick tweed until they bleed." Such contempt.

She rattles on impassionedly, getting balmier and balmier, despite lots of Valium and the ministrations of her husband. To his credit and hers, their scenes, listless or hysterical, are well-acted. And if any one followed the other in a dramatically consistent fashion, and if the momentum were allowed to build, well then this might have been really something. But "Plenty" is nothing for me.

PLENTY (R) -- At area theaters.