Michelle Williams and Luke Kirby, stars of Take This Waltz.

Thursday night’s Sunshine Cinema screening of Sarah Polley’s film Take This Waltz was sponsored by Forevermark and Crystal Head vodka. A romantic tale of infidelity and emotional rubble sponsored by diamonds and booze? By that same token, does there somewhere exist an all-you-can-eat pig roast underwritten by wet naps and burning shame? It all seemed a heartbreakingly serendipitous manifestation of the universe’s fuzzy feelings for humanity.

The film, Ms. Polley’s sophomore effort, tells the story of a young wife (Michelle Williams), lured away from her happy marriage to cookbook writer Seth Rogen by a rickshaw driver (Luke Kirby). We won’t spoil the ending for you, but Michelle Williams really is terrific, and we’re pretty sure there exists an entire market of people wanting to see Mr. Rogen emotionally decimated.

Ms. Williams looked stunning in a fitted black Altuzarra dress and white Givenchy stilettos. Disturbingly vivid thoughts of footwear theft banished, The Observer asked if she thought Take This Waltz shared a bloodline with classic romance movies. “I don’t think it’s up to me to decide. I make it, and I love it, and I invest in it, but it’s up to other people to figure out where it fits in their hearts.”

The director, Ms. Polley, summed up her celluloid inspirations for the film thusly: “A lot of early Woody Allen movies. They’re not exactly romance movies but they talk about relationships in a way that feels authentic and yet a little bit fantastical. I find it really hard for films to feel genuinely romantic.”

Ms. Polley’s fellow Canadian and leading man Mr. Kirby swung by briefly on his way to Georgia where he’ll be shooting the Sundance Channel legal drama Rectify. While Mr. Kirby was spirited away before the film started, The Observer was able to secure a post-screening moment with Griffin Dunne while ascending the Sunshine’s staircase. “I thought Michelle was just amazing, just a fearless actress. It was very complicated and sad, ” he told us. We concurred. Of shooting Martin Scorsese’s dark 1985 comedy After Hours, we asked Mr. Dunne if he had then an inkling of what the relatively desolate SoHo would become. “Not a clue. I live there now and I don’t recognize it. There’s not one person who lives there, it’s all tourists.” Mr. Dunne unchained his bicycle. We were sufficiently impressed. “Essex is that way, right?” he inquired, pointing eastward. Indeed. “Maybe I’ll see you over there!”

The ‘there’ to which Mr. Dunne referred was hipster citadel Sons of Essex, to which guests were making their collective way. The Observer hoofed it over, feeling only a bit slighted when Mr. Dunne breezed past us at a stoplight.

Sons of Essex was already buzzing upon our arrival. Michelle Williams and squeeze Jason Segel sat with friends in a corner banquette. Mr. Segel, looking both dapper and jovial, maintained the lowest profile possible for a man of 6’ 4”. He confessed to us that he had not seen Take This Waltz yet, before politely slipping outside. When he returned, it was with a series of gift bags from Brooklyn toy store Acorn, later spotted on Ms. Polley’s arm.

Of assuaging her nerves, the director told us, “I actually didn’t stay for the screening. You suffer too much from the things you would do differently. Plus, it’s my second film, so I’m still learning a lot.”

Servers made their way through the now-packed space, ferrying nouveau comfort cuisine to the farthest corners. Pork belly sliders and truffled pizza were on everyone’s lips, in more ways than one. Guest sipped Stella Artois and Crystal Head signature cocktails (dishearteningly light on the Crystal Head, we might add), some flocking to watch the NBA game being projected at the back of the room. Models-cum-tourists posed listlessly for friends’ iPhones, all pouts and tanned limbs.

Philanthropist/socialite/headband enthusiast Arden Wohl was on hand, too, in a white Donna Karan dress dappled with red kisses. Her two cents on the film? “I thought it was really great. Sarah Polley’s really talented, and she has a really true friendship with Michelle Williams. You can really sense that... It’s so nice to see women directors.”

PR tycoon and Take This Waltz publicist Peggy Siegal filled us in on her busy summer plans (promoting a roster of films concerning both Diana Vreeland and Katy Perry) and her thoughts on Ms. William’s personal life. “I’m very happy she’s dating someone named ‘Segel.’ I keep telling him we’re related.” But are they even spelled the same, we inquired humbly? “No, but it doesn’t matter. I keep telling him that in the ancient Hebraic religion, the Cohens were the rabbis, and the Siegals were the cantors. So somewhere, way back when, thousands of years ago, I am related to Jason Segel. And he knows that!” Mr. Segel was unavailable for comment.

Lower East Side, invitation only.