Matthew Broderick, a longtime pal of Lonergan who appeared in the writer-director's film "You Can Count on Me," plays a dullish, sparkle-free astronomy teacher at the Hayden Planetarium who stumbles into an extramarital affair (with Catalina Sandino Moreno, the Oscar nominee of "Maria Full of Grace"). J. Smith-Cameron — Mrs. Lonergan, ironically — plays a wife you'd want to run away from.

The tone of the play is serious and life-like, peppered with stingy zingers and measured sarcasm. For Broderick, the role is very heavy-lifting, Hamlet-sized and full of protracted speeches. Just getting through it is a major feat of memory.

One speech, he said, "is three solid pages of script — with very wide margins."

"He's perfect for it," Lonergan declared at the party. "I tried to write this play 20 years ago and couldn’t make it work out, but, when I was working on it, I was thinking, 'Gee, I wish Matthew was in his 40s,' because I always thought it was a good part for him. Now, here we are in our 40s so…"

— Harry Haun