"Union Square," Nancy Savoca's long-awaited return to feature filmmaking, is the tale of two sisters divided by temperament, geography and class. The first one we meet is Lucy (Mira Sorvino), a whirlwind of attitude and emotion who blows into Manhattan with her smartphone, her lap dog and no small amount of emotional baggage. After a bunch of angry texts and phone conversations with her married lover (who is never seen) and a bout of extreme shopping in discount emporiums, Lucy arrives at the apartment of her sister, Jenny (Tammy Blanchard).

The welcome could hardly be chillier.

Jenny, it seems, has turned herself into a point-by-point rebuttal of everything her sister represents. If you listen closely, you might hear a hint of their working-class Bronx background in Jenny's voice; with Lucy, it's about as subtle as a car horn in heavy traffic. Jenny, whose future in-laws think she grew up in Maine, acts out a daily caricature of repressed, genteel propriety, words that no one would think to apply to her sister.

It has been three years since Jenny and Lucy last saw each other, and the details of their estrangement are vague. But Savoca is less concerned with shoehorning the characters into a neat story than in watching them bounce around in a confined space filled with unruly, unwelcome feeling.

As Thanksgiving approaches, secrets spill out, grudges are aired and a great deal of organic vodka is drunk.

Sorvino has been too scarce a presence on movie screens in recent years, and her brassy, heartfelt performance cries out for melodrama on a larger scale. Savoca ("True Love," "Dogfight," "Household Saints") makes the most of limited resources — a small cast, a few locations, a digital camera — and she, too, could have used more room to stretch out. But "Union Square" has a lively, nervous energy and an expansive sympathy for the mismatched women at its heart.