Rinne Groff’s imagination runs way ahead of her implementation. Though she seems to have everything going for her – a resume that reads like a “top 10” of downtown theater companies and plum play-placement all over town – something isn’t quite working. In her most recent piece, “What Then” at the Ohio Theatre, an uneven cast and an unsteady application of whimsy reveal Ms. Groff’s own bumpy patches.

For every subtle (one character’s favorite word) gesture, Ms. Groff follows up with a nail-on-the-head caption. Her writing, alternating between bold strokes and dreary conventional stretches, seems to lack the strength of its own experimental convictions. Every time she seems to be escaping the fetters of traditional drama, she lets some badly executed, old-fashioned structure drag her back to the ground.

On an enviably clean kitchen set, made all silvery and Scandinavian by set designer Jo Winiarski, a married couple bicker. In the first of the show’s blatant gestures, the husband, Tom (Andrew Dolan), is dressed in a black tracksuit, while his wife, Diane (Meg MacCary), wears white.The stage is set for mystery, with Tom toting around a titanium briefcase that mustn’t be opened, and Diane lost in memories of their past. We get it long before the show has finished making the point: He’s all business and she’s all nostalgia, and there’s a building menace in their lives.

At first, nothing could be more domestic: Diane fesses up to quitting her job; Tom rails against her for her immaturity. Off-the-cuff complaints about the weather and a dried-up local lake reveal that their posh house exists in a wasteland of industry’s own making. Tom, defensive about all his “projects” (which may have had something to do with toxic water and the government-issued gas masks) doesn’t want to hear about Diane’s new “work” and he hates that she sleeps 15 hours a day. Once she admits her new “dream job” is literally that – a sleeping hallucination that she is an architect – Tom storms out.

And in storms Tom’s daughter, Sallie (the astonishing Merritt Wever), a drug-addicted, alienated whiner. With incredible energy for such a waster, Sallie complains about unfair housing codes that dare to ask her for a blood test. After a callous plot twist, where she has her boyfriend Bahktiyor (Piter Marek) steal the sleeping Diane’s blood, Sallie believes she has finally gamed the system. But that’s before her dad buys drugs off Bakhtiyor, Bakhtiyor begins to share in Diane’s dreaming alternate reality, and a nasty chemical snow signals that the end times are nigh.

Director Hal Brooks, who lets his cast work a bit too slowly, never establishes a visual correspondence with his playwright’s material. Other than some woozy lava-lamp glow during Diane’s weirdest hallucinations (thanks to lighting designer Kirk Bookman), the set and characters stay bright and banal. Part of Mr. Brooks’s trouble lies with Ms. MacCary, who is miscast as Diane. Ms. Groff has made Diane a kind of saint whose intense sensitivity makes her identify with the dying earth. But Ms. MacCary is far too well-scrubbed to be haunted, and her most beatific expression seems to be one of mild surprise.

While her strange, convoluted plot manages to establish its own, nonsensical internal logic, Ms. Groff has a much harder time with character (Ms. Wever has to create her gorgeous one from scratch), and has a terrible struggle with tone. In moments of extreme emotion, she borrows cleverly from Woody Allen, letting her characters sing inexpert songs of apology and love to each other. But the transition from earnest environmental allegory (Diane slips further into sleep as the lake dries up outside) into postmodern silliness never glides as it should.

Ultimately, Ms. Groff trips over her own desire to be clear. In “What Then,” the narrative only serves to startle us awake from an occasionally compelling dream. Another production, with a director more interested by ambiguity than didacticism, might have found a necessary complement in Ms. Groff’s musings. But in this gleaming room, with every foible exposed and every statement pedantically delivered, Ms. Groff and her characters can’t get lost in the shadows – the shadows that give a picture its weight.

Until January 28 (66 Wooster Street, between Spring and Broome Streets, 212-966-4844).