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It’s tough to say if the script for Heisenberg, Signature Theatre’s new play going on now until Nov. 11, was workshopped too much or not enough.

A chance encounter that isn’t really by chance, a May-December romance where the attraction is almost beside the point, a talky show where you don’t believe a word of the dialogue, this 90-minute production somehow still dances its way to your good side despite having two left feet. Carrying it across the finish line are a pair of able-bodied performances, Joe Calarco’s direction, and a story that doesn’t bite off any more than it can chew.

Heisenberg, which somehow spends its time concerned with neither German theoretical physics nor with Albuquerque-based blue meth, kinda floats through itself, with the undeniable whimsy of a balloon loose in the wind.

Georgie Burns (Rachel Zampelli), an American woman in her early 40s, meets Alex Priest (Michael Russotto), an Irishman in his 70s, in London, where they both live. They strike up a connection, but you wouldn’t really call it a rapport, because mostly Georgie chews Alex’s ear off, especially for their first several interactions. She accepts his handkerchief, Googles him, shows up unexpectedly at his work, and essentially strong-arms her way (sounds weird, but that’s what she does) into a date. Georgie, one of those deliberately eccentric and spontaneous women who pepper rom-coms, and Alex, a creature of habit so ingrained that he’s made the same walk home for more than 20 years, are a study in contrasts … so you know they’ll wind up in bed.

Georgie is less than honest, and her motives are far from pure, but she’s more than redeemable in Zampelli’s hands. The actress gives her flighty, babbling character a humane delivery; she builds Georgie out of durable materials, no matter their strange shape. And Russotto doesn’t take long to find the beating heart of Alex, filling his silences with emotions and his speeches with wit. The actors both appear at least a decade too young for their roles, but there can be no complaints about their chemistry. Even if you’ve seen Zampelli and Russotto in other D.C.-area productions, they will show you some new shades here.

That’s good, because Simon Stephens’s script doesn’t do them too many favors. Stephens, who did a poor job adapting for the stage the great novel The Curious Incident of the Dog in the Night-Time, all but has his characters doing backflips into Unbelievable Land. They talk the way only people in a play talk, deal with problems in ways that only characters up on stage would do, and generally play romantic variations on Heisenberg’s uncertainty principle — a theorem about which there is absolutely nothing romantic.

There’s a Chekhov’s tango, lots of talk about the past and diaries, and a messy bit of money where it shouldn’t be. Without giving away any significant spoilers, the experiment leads to mixed results.

The end result is a true theatregoer’s play. Don’t make it your first dramatic outing of the year, but don’t shy away from it, either. Does that sound uncertain? Well, that works out.