Smaller movies often get lost in the shuffle when you’re covering an event as huge as the Toronto International Film Festival, so I’m glad I got to see Nancy Savoca’s “Union Square” beforehand in New York.

Mira Sorvino gives perhaps her best performance as a Bronx woman on the verge of a nervous breakdown. She shows up announced at the Union Square condo her long-estranged sister (Tammy Blanchard) shares with her fiancee on the eve of Halloween.

The sister has put their troubled childhood behind them to lead a more genteel life — and even claims she comes from Maine — but lots of secrets gets dredged up.

While there are others in the cast, including Michael Rispoli, Daphne Ruben-Vega and Patti Lupone, this is basically a two-woman movie with a pair of terrific performances that benefits from an abbreviated running time.