LOOSE ENDS -- At the Arena through March 11.

Michael Weller, who took care of the 1960s in "Moonchildren," has polished off the '70s in "Loose Ends," and done it no less effectively by using affection and humor.

This devastating play, which Alan Schneider has directed at Arena Stage, traces the relationship of a nice young couple from a meeting in 1970 through a marriage to a post-marital reunion in 1979. The niceness, in this case, means that they are well intentioned, self-sufficient and in love; they don't have a single one of life's recognizable problems, such as illness, poverty or even any responsibilities other than to their own happiness.

And they manage to mess it all up themselves, for a peculiarly vague concept of freedom that is pure 1970s.

Weller has such a good ear, and the actors and director are so finely attuned to it, that a panoply of familiar 1970s "options" is funny without being trite. Celia Weston as a new-style New Hampshire farm wife, Robin Bartlett as an enthusiast for whatever comes along, John Wylie as an arbiter of New York taste, and others deftly present the conventional roles of the decade. (This is not the Arena company; nearly all the actors are playing Arena for the first time.)

Strangely, it's not these portraits that condemn the era. Gracelessly fashioned as these invented "lifestyles" are, they have already become patterns into which people can more or less fit themselves. It's the hero and heroine, and she in particular, who can see beyond these choices and make up anything they want for themselves, who flop.

Roxanne Hart and Kevin Kline, as the young couple, meet with musical-comedy freshness (except that they are stark naked -- Arena Stage has discovered nakedness this year, and every play seems to be at least one costume short). They're in Bali, carefree young tourists who make love first and trade last names later. They re-meet in America, marry, decide not to pursue standard careers, fashion successful careers on their own terms, talk about love, talk about having a baby.

Slowly, they begin to drive us mad. At first it's cute that they prattle away, mouthing the theory of open marriage while embarrassed to admit they only want each other. Years later, when she's still at it, not telling him that she's pregnant because "I want to get comfortable with the situation first so I know how I feel about it," it's infuriating. She is worse at this than he, because she's the directionless leader for them both.But finally, after nine years of discussions beginning "Do you want to talk?," there's nothing left to say about themselves and their precious feelings.

Weller, with his domestic comedy, has managed to finish off the concept of personal freedom, along with the decade.