“Nobody Walks” follows a sexually voracious intern who turns a family upside down by her mere presence. It’s the kind of erotically overheated story that skimps on nuance and realistic moral boundaries.

Is it any wonder the woman behind the “first time” ad for President Barack Obama helped pen the screenplay?

Lena Dunham flashed both talent and restraint with her celebrated indie “Tiny Furniture,” and her HBO series “Girls” became a minor sensation in record time. With “Nobody Walks,” she reveals a tone deaf approach to relationships and the intricacies of marriage.

Olivia Thirlby stars as Martine, a budding sound design artist who lucks into an internship with Peter (John Krasinski), an experienced sound editor. Together, Martine and Peter use a cacophony of clever sounds to bring a short film about ants to life. Peter may be married, but he’s drawn to Martine’s … talents. So, too, are other characters in the film, none of whom consider the emotional ramifications of a night spent with the pixie-esque artist.

And so it goes in this drab, dramatically inert affair.

“Nobody Walks,” co-written by Dunham and director Ry Russo-Young, ultimately has nothing to say. Nada. Thirlby, an appealing presence in films like “Juno” and “Being Flynn,” can’t find her character’s inner conflict or reveal how she compartmentalizes her behavior. Krasinski is similarly adrift, although he can cast blame on a rudderless script.

Sexual hunger can drive even a spare, detached drama. Peter’s marriage, which on the surface appears solid, could reveal the kind of weaknesses that make Martine’s presence even more provocative. Dunham and Russo-Young bypass all these potential paths, settling for a humdrum round of sexual roulette which ends in dispiriting fashion.

“Nobody Walks” features plenty of sex but lacks passion, proving Dunham still has a thing or two to learn about both political ads and on-screen infidelity.