Annie and Darren, the cutie-pie thirtysomething Los Angeles couple whose marriage is gently dissected in Katie Aselton's impressive directorial debut, The Freebie, have the perfect marriage.

That is, if by marriage you mean a sexless, comfortable cohabitation filled with baby-snuggles and board games.

"I love you, buddy," Darren (Dax Shepard) tells his wife of seven years early in the story. As lovey-dovey as they are, neither can remember the last time they had sex.

Annie, who is played with an easy, cool - though never detached - grace by Aselton, is infinitely patient. One night, she tries to spice up the bedroom by putting on a sexy bikini.

Darren is unmoved. He'd rather stick to their bedtime routine - crossword puzzles.

Reminded of their flagging matrimonial libido at a dinner party, Annie and Darren finally come up with a plan: They'll each reboot their sex drives by having a one-night stand with a stranger.

Thus begins The Freebie, a not too funny, not too sad, largely improvised dramedy about two nice people who both succumb to the seven-year-itch and live to regret it.

Annie and Darren are no Simone de Beauvoir and Jean-Paul Sartre, that famed French couple who flaunted their supposedly fabu, way-cool existential open relationship.

Our heroes know from the get-go their plan is stupid, yet they press on.

In the film's best sequence, Aselton cuts between the two as they make their fateful choices. Cleverly, she never shows us how the night ends.

The fallout is tense, and at times difficult to watch.

Aselton, who made The Freebie with a tiny budget, is a member of the Duplass Brothers comedy team - she and husband Mark Duplass costarred in The Puffy Chair and are featured in FX's semi-scripted sitcom, The League.

She brings the Duplass' zeal for improvisation to The Freebie, which she made with only a six-page outline. The gamble pays off: The cast, which includes Bellamy Young, Sean Nelson, and Marguerite Phillips, improvise their parts with subtlety and wit.

Shepard gives a solid-enough performance, but his Darren is so ingratiatingly nice, so fulsome - and so fantastically asexual - it's hard to believe he's ever had lust in his heart. He's like a child playing house.

As a serious morality tale, The Freebie leaves a lot to be desired. But with its brisk pace, assured direction, and lean storytelling, it is a fine slice-of-life story.