Noel Coward's Blithe Spirit is about as frothy as theater gets. It's 1930s baronial Scotland. People dress for dinner and drape themselves languidly over the furniture drawling things like "Anyone can write books, but it takes an artist to make a dry martini." You get the feeling that marriage required less soul-searching then, but a great deal more skill at repartee: the middle-aged Condomines usually pass the time swatting each other's witticisms, and as the play opens, they've arranged a special diversion for their privileged, irreverent selves and a few friends — they've invited the local spiritualist/nutcase over for dinner and a séance. To Mr. Condomine's surprise, the evening conjures the spirit of his departed first wife. As comedy (or, for that matter, tragedy) would demand, he begins to find her more alluring than his present spouse.

Imagine Ethan Frome as farce, and that pretty much sums up the rest of the plot: boy has girl, boy meets girl, boy is condemned for eternity wishing he'd never met either girl.

For a play as weightless and evanescent as this one, it has some delightfully good ballast anchoring it to this world. The heavy set, of damask and polished wood, would probably fool the queen herself (it is appropriately stocked wall to wall with dead ancestors and assorted taxidermy, all gazing on the proceedings like a sort of gallery of spooks). The costumes come from whatever extraordinary reservoir the Purple Rose draws from when it does these midcentury period pieces (I was equally infatuated with last summer's Born Yesterday wardrobe, from roughly the same era). And for all the fluffiness, it clocks in at a very nonfluffy three acts and two intermissions.

The real assets of the production are the cast, for while Blithe Spirit is farce, it wants swift, delicate understatement rather than in-your-face buffoonery. And, mostly, that's what it gets. Sandra Birch as Madame Arcati (the medium) is the only one who plays her part a bit too broadly — I would argue that her success in actually conjuring two spirits suggests that the character is really a consummate professional rather than an off-the-charts lunatic (the interpretation Birch favors). Yet, for all that, she's fun: let's just say that this theater is a bit too small for her. The rest do a great job of effortlessly keeping the dialogue aloft. Special treats are Terry Heck, who sports a particularly elaborate Scottish accent, and Malcolm Tulip, a gifted physical actor who reins it all in to play a part defined by word calisthenics — and is rewarded with a great moment of physical comedy at the end.

Blithe Spirit continues its summer run, Wednesday through Sunday, through August 30.