Nobody Walks is one of those fish bowl films: an idea is tossed in like a crumb, then we wait and watch what happens.

This dark story unfolding in sunshine wonders what might happen to a beautifully blended but bored California family when a pretty young thing shows up. The copacetic ensemble toying with all the emotions include John Krasinski, Olivia Thirlby, Rosemarie DeWitt, Justin Kirk, India Ennenga, Rhys Wakefield and Dylan McDermott. That no one will come out unscathed is a given.

Indie director Ry Russo-Young, who continues to favor ethics-testing stories of the heart, co-wrote the script with Lena Dunham, Hollywood’s current it girl, with HBO’s Girls her most visible project at the moment. The story is loosely constructed, and like that crumb in the bowl, the dilemmas that surface tend to float rather than head to any particular destination. If you allow yourself to drift with it, rather than get frustrated by all the non sequiturs, Nobody Walks becomes a more enjoyable film.

Here’s the setup: Martine (Thirlby) is an experimental artist whose latest film project seems to involve bugs eating other bugs, or copulating — hard to tell whether she’s shooting love or war — which fits with the movie’s themes. Her kiss-off of the boy she leaves behind in New York as she heads to Los Angeles starts to sketch in the way Martine uses people.

With that opening salvo, Martine arrives in the artistic ecosystem of Silver Lake, where she’s to spend a few months with friends of a friend. Julie (DeWitt) is a therapist; husband Peter (Krasinski) is a noted sound designer with a soundproof studio next to the pool house where they are putting up Martine while Peter helps with her film. Kolt is Julie’s teenage daughter, precocious but distracted by a major crush on her stepdad’s assistant, a hunky David (Wakefield). Her father, Leroy (Dylan McDermott), still stops by for dinner. Julie and Peter have a cute young son, but he is so nonessential you wonder why he’s there. There is no confusion about how Julie’s screenwriter-patient Billy (Justin Kirk) will factor in; he flirts and flatters his way through each session.

Initially the family welcomes Martine with open arms, she’s a relief from the stasis that has overtaken their lives. Her exotic look and introspective style create a kind of seductive force field without her even trying. But soon she is trying. Though no one is left untouched by her charms, the most important one to snare is Peter; his sound expertise can make or break her film.

We see it before he does — that telegraphing of too much too soon is one of the film’s weaknesses — as Martine begins to shift the older-brother attitude he evinces to something so serious it could rupture the family.

There is a languor to everything that happens, except for the sex, which is steamy and stolen. Everything about the film and its characters feels lush and ripe, ready for picking. That sensual feel heats up as passions are provoked and resentments rise.

Thirlby has a way of moving through scenes and riffling emotions that makes it easy to believe she will leave destruction in her wake. Krasinski has the harder job in Peter. With so much of his interior life rocking along on the surface, his self-destructive urges seem to come out of nowhere, and their trajectory is even more difficult to buy. Just one of several imperfect, yet interesting characters in this imperfect, yet interesting film.