Tammy Blanchard, left, and Mira Sorvino in UNION SQUARE (Gerardo Somoza/Dada Films)

On a sunny afternoon in Union Square, a distraught woman laden down with shopping bags from discount department stores was yelling with a broad Bronx accent into her cell phone. And then moments later I went into Nancy Savoca’s Union Square, and saw the exact same scene, only the on-screen manic blonde wearing snazzy boots was played by Mira Sorvino.

She’s Lucy, and is very nervously out of place in Manhattan, but she shakes off tears, puts the phone back in her purse, and heads toward an upscale loft apartment nearby. At first it seems that Sorvino might be repeating her ditzy prostitute from Woody Allen’s Mighty Aphrodite (1995), but one of the recurring, insightfully clever tricks of this somewhat uneven film is that initial appearances mislead. Lucy is savvy enough to hunt down the manager of an organic food delivery start-up on Facebook—her younger sister Jenny (Tammy Blanchard). They haven’t seen each other for several years, so the uptight Jenny is considerably disconcerted to find Lucy on her doorstep unannounced. Not only is Lucy loud, she unzips a noisy little dog, Murray, out of her big bag. After Lucy pleads, with a megawatt charm but without explanation, to stay over a few days, Jenny relents and tries to box her sister into her quiet, organized loft life, shocking Lucy by insisting on no smoking, no shoes inside, and no meat eating.

Jenny’s vegan lifestyle becomes more of an issue because Thanksgiving is looming and she is already stressed out prepping to host her future in-laws for the first time. Savoca rocked the conventions of the familiar family gathering movie in her debut True Love (1989), but she at first veers away from most of the usual holiday tensions when the future in-laws cancel. This gives Jenny some wiggle room to keep fiancé Bill (Mike Doyle) believing that her family is from Maine, as she has been telling him. That becomes more difficult when another blast from the past shows up, the sisters’ old friend Sara (Daphne Rubin-Vega). When she goes out clubbing with Lucy, she starts sounding more like Jenny from the block.

Jenny has, in effect, been passing for a WASP like Bill, holding her emotions, roots, and family deep inside, hidden from even herself. But as Jenny’s wall starts to crumble (rejection of her in-law’s unflattering traditional wedding dress is a start), Lucy drives through to her heart the real reason she came downtown, to show her a video she posted on Facebook of their ill mother Lucia (Patti LuPone, pulling out all stops as a Bronx Italian matriarch). Even Murray the dog sets off a teary guilt trip for Jenny. Lucy has borne the brunt of their dysfunctional family for all the years Jenny was in denial and cut off from the family, but she might not be able to hold it together on her own anymore

Just when the movie seems to be going in the direction of an amusing family Thanksgiving comedy, it zings sharply (and a bit awkwardly) into exposing raw emotions from the painful wounds the sisters share from the past. The authenticity of these feelings smoothes over some confusing explanations about the sisters’ lives, especially Lucy’s, who keeps pulling out surprising revelations like a magician. The tears are balanced by satirical scenes from “Salon Divas,” a fictional reality TV show seen throughout the film (and in a post-credit addendum), where loudmouths quarrel and then natter on about the importance of family above all. The lovely closing ballad reinforces this theme—Madeleine Peyroux crooning Warren Zevon’s last song released before his death, “Keep Me in Your Heart.”