Tom Dolby’s quiet dramedy starts as real-estate porn: shots of a mini-manor, with interiors that would make Martha Stewart moan with envy, set on a sparkling lakeshore (Tahoe, as it happens) for which most state tourism boards would sell their grandma. It morphs, gently as a sunset, into something like an A.R. Gurney play transposed west—an autumnal examination of upper-middle-class mores in the face of bittersweet change.

As her family gathers here over Labor Day weekend, as they have forever, Celia (Patricia Clarkson) is secretly mulling whether to sell the site of so much history. (The spoiler’s in the title.) This is only one secret in the web of possible emotional flashpoints connecting her, her husband, her two adult sons, their significant others, and a few other friends. (The characters include a TV actress played adorably by Jayma Mays, a sort of baby Heather Graham; also appearing are old pros Judith Light and Mary Kay Place in tiny roles that’ll leave you yearning to see more of them.)

This family’s usual mode of communication is unwitting (or are they?) put-downs wrapped in gentility; Last Weekend ’s subtext is how wealth becomes a cozy bubble that enables you not to have to consider whether your words sting. Clarkson, of course, from The Station Agent to Six Feet Under to Far From Heaven, can ring changes on subtly observed brittleness like no one else. Not everyone in the cast handles so deftly Dolby’s slightly pat script; they’re not completely able to build real people out of those characters given only plotlines in lieu of personalities. But this is Clarkson’s movie. They’re moons around her neurotic planet, all of whom raise the question: Does money make you this way, or does it merely let you get away with it? Opens Fri., Sept. 26 at Sundance Cinemas. Not rated. 94 minutes.

gborchert@seattleweekly.com