Despite the vast range of stories that have been mined from the Sixties, a crucial one that's been neglected is that of women who came of age before the Pill. A Walk on the Moon is the rare movie to take on the subject. The directorial debut of actor Tony Goldwyn (The Pelican Brief, Nixon), Moon is set in the summer of 1969, coinciding with the first moonwalk and Woodstock, two watershed events that have been so often employed as metaphors that their power has been horribly diluted. That's too bad, because as sentimental as it is, this picture contains the right ingredients to distill a compelling drama about the complexities and contradictions of women's lives.

At the story's center is Pearl (Diane Lane), a 31-year-old mother who has an affair with a free-spirited salesman passing through the working-class Catskills resort where she is vacationing with her family. Pearl wouldn't describe herself as unhappily married, but as the summer progresses she is pulled toward the freedom she sees younger women enjoying. (She is practically the only person at the resort who doesn't find hippies skinny-dipping in the lake to be scandalous.) Pearl is also envious of her fourteen-year-old daughter, who is dating for the first time and entering womanhood at the dawn of the sexual revolution. But her envy is tinged with genuine concern: She doesn't want Alison (Anna Paquin) to become pregnant and married too early, as she was at age seventeen.

Neither Pearl nor her daughter can possibly imagine how women's lives will change when birth control becomes commonplace. In its best moments the movie shows how middle-class women were punished by the consequences of their own sexuality, often becoming mothers before they were grown up themselves. Moon also examines how the limits placed on women hurt their families. To her credit Pamela Gray did not write a screenplay (it won the Samuel Goldwyn Award at UCLA's film school) that blames men. Pearl's husband Marty (Liev Schreiber) saw his chance to go to college extinguished when he got Pearl pregnant. A TV repairman who works in the city while his family vacations, he, too, has experienced the curtailing of his dreams.

Unfortunately the movie demures from placing Pearl's dilemma in a distinct historical context, relying instead on mere allusions to Vietnam and other touchstones; its characters don love beads and take a side trip to Woodstock. Lane (TV's Lonesome Dove) gives an appealing, down-to-earth performance as Pearl, and Paquin is powerful as Alison - not easy roles to pull off in a movie that looks and feels so artificial. Its well-appointed sets (every shot calls attention to period details) are drenched in nostalgia. As is the score, a collection of Sixties chestnuts, including the Grateful Dead's Uncle John's Band and Bob Dylan's Subterranean Homesick Blues. (A wrong note: Broadway star Tovah Feldshuh, who infuses Pearl's mother-in-law with a tiresome saintliness.)

As the guy Pearl falls for, Viggo Mortensen drips with sex appeal. He'd attract almost any woman. But without a more complex rendering of what she's going through, Pearl seems like, well, any woman.