See if you can guess where this will lead: Maggie (Cameron Diaz) is something of a ditz, perennially irresponsible, reckless and promiscuous. Her sister Rose (Toni Collette) is a workaholic lawyer who's just started to date her boss, oh so tentatively, because she knows it's a bad idea. Maggie blows into town (Philadelphia), and, as she has no place to live, she crashes at Rose's for a few days that will turn into weeks. And oh yes, the first scene shows Maggie's 10 year high school reunion, where she's having sex in the bathroom, under Garbage's "Stupid Girl."

In Her Shoes is formula of the quality sort. And it comes with a pedigree that indicates its bent. Directed by Curtis Hanson (L.A. Confidential), written by Susannah Grant (Erin Brockovich), and based on ex-Inky scribe Jennifer Weiner's novel, it's a multigenerational chick flick. The sisters must come to terms not only with one another, but with the difficult background that has produced their movie-styled dysfunction. That is, their conflict is repeatedly framed through snapless one-liners to indicate character "interests," as when Rose suggests Maggie look for a job ("There's a whole world of commerce out there that has nothing to do with sex") or Maggie uncleverly deplores her sister's fashion sensibility ("1994 called; it wants its hair scrunchy back").

But of course, for all their dissonance, the sisters really do share basic values and aspirations, only hating each other and themselves because they're not more like each other. They share a much-missed dead mom and a pathologically passive father, Michael (Ken Howard), whose story becomes more complicated soon enough. His second wife, the odiously named Sydelle (Candice Azzara), is as annoying as a tacky snob can be, resenting her husband's family and doting on her own daughter (whom the left-out-feeling sisters call "Mymarsha," after Sydelle's own possessive designation).

In their bonding against Sydelle, Maggie and Rose demonstrate a certain sameness, at least in their capacity to begrudge and judge. Their similarity is underlined as well in their affection for shoes. These come up repeatedly, as objects of desire and signs of emotional health. Rose has a closet full of them, expensive, neatly arranged and mostly unworn. As Maggie's face reveals her simultaneous envy and approval, Rose's explanation is at once self-aware and pathetic: "Shoes always fit," she says, "I treat myself when I feel bad." A reverse shot of the frankly stunning collection indicates that Rose feels bad frequently. And beside that, as she puts it bluntly to her whiny sister, "I don't have room in my head for your problems right now."

The shoes also mark the sisters' fundamental differences in attitude, self-regard and impulse control: Rose preserves them, Maggie makes use of them. Though Rose declares the shoes off limits, as soon as she leaves for work, Maggie's all over them (after she's done rifling through Rose's drawers in search of cash). The sisters clash loudly when Rose discovers Maggie using something else Rose considers her property. By this point, you've learned that Maggie has reasons for her incessant screw-ups (namely, she's dyslexic and insecure, having grown up feeling inferior and unloved and abandoned, and yadda yadda yadda). And so Rose's furious, kick-ass dis — having to do with Maggie's stupidity — actually seems cruel, and Maggie's departure somewhat sad. This even though their barely repressed rage at one another has been making them and you miserable for the past 45 minutes.

So begins part two of In Her Shoes, wherein Maggie discovers the existence of a grandmother, Ella (Shirley MacLaine), and the sisters find even more grounds for their conflicts, with each other and with the world. Ella lives in a Florida retirement community, and is as cynical and tough as Maggie believes herself to be. Their even-matchedness leads both to soften up some, which is not to say they meet precisely halfway (though Ella does invite a couple of fellow retirees over to drink Flirtinis and watch Sex and the City, in an effort to engage Maggie's interest).

Ella and Maggie do, however, understand one another well enough that their evolving relationship elicits Rose's jealousy. That is, after she learns of the relationship at all, as Maggie essentially disappears from Rose's view, leaving her in something of a puddly depressed mess. Looking to reinvent herself, she quits her lawyering job to walk dogs instead, and takes up with a former colleague, Simon (Mark Feuerstein), who appears genuinely nice. Thusly, as they separate and refind one another, Rose and Maggie are left crushed and breathless beneath the weight of formula, quality or no.

In Her Shoes Directed by Curtis Hanson A Fox release Opens Friday at area theaters