It would not be hard to imagine a glass menagerie on the breakfront in "Uncle Frank," or, somewhere in the distance, a horn being honked by a streetcar named Desire.

In both its ability to find humor in tragedy and in its themes — the strength of Southern matriarchs, fathers who try to suppress gay sons' identities, naiveté that provides an opening for acceptance — Alan Ball's "Uncle Frank" feels indebted to the great Tennessee Williams. You could think of it as an homage, or as an autobiographical piece in which Ball recognized bits of his own story in the playwright's enduring truths. (Coincidentally, both "Frank" and this week's "Happiest Season" have scenes with closeted characters enduring uncomfortable Christmas gift openings.)

Mostly set in a rural South Carolina home in the 1970s, "Uncle Frank" has a theatrical quality that extends beyond the Williams references. If he were alive, I could see him crafting roles for the great women who play zesty supporting characters: Margo Martindale as the big-personality mother of Frank, a gay man forced out of the closet on a visit to family. Lois Smith as Frank's grandmother, who is loving even if she can't overcome her bigotry. Judy Greer as Frank's sister-in-law, who believes every '70s stereotype about homosexuality but whose good heart makes her oddly endearing. Sophia Lillis as the niece through whose eyes we view events. (Minnesota native Steve Zahn is also excellent in a small but key role.)

In description, "Uncle Frank" sounds like a tonal nightmare, but Paul Bettany's quiet, calm performance as Frank glues everything together. Bettany's idea seems to be that Frank stays in his delicate bubble by making himself as small and invisible as possible when he's around family. That acting choice pays off in the moving moment when Frank and his mother finally chat about who he really is and Bettany, seated and seemingly trying to roll himself into a ball at the start of the scene, suddenly opens his body up.

Ball is known as a writer — he won an Oscar for "American Beauty" and created "Six Feet Under" — but he makes smart visual choices as a director, effectively using filming locations in North Carolina. There is, for instance, a symmetrical forest of tall, slender trees that "Uncle Frank" turns into a kind of mythic place where the characters go to figure things out.

His one mistake is casting Peter Macdissi (Ball's real-life partner) as Frank's boyfriend. Macdissi's cartoony performance doesn't fit in this movie — charitably, maybe that is the actor's intent, since Frank's family views his Saudi Arabian character as if he's an alien — and his bizarre wig makes it look like there are a couple beavers piled on his head.

Tragic events pile up in the final scenes of "Uncle Frank" and the characters fail each other. But Ball imbues them with a hopefulness that brings to mind Williams' Gentleman Caller in "The Glass Menagerie," who says, "Being disappointed is one thing and being discouraged is something else. I am disappointed but I'm not discouraged."