How many universes might lie within and without us? And how many ways (perhaps infinite) could our lives and loves turn out in different ones? That’s the big idea examined in what might seem a small play: Nick Payne’s two-character piece Constellations, now running in a Stage III production in Florida Studio Theatre’s intimate Bowne’s Lab Theatre.

As far as staging goes, it doesn’t get more basic than this: a man (Chris Tipp) and a woman (Alexis Hyatt) standing there talking, with stars twinkling behind a curtain for a backdrop. But in the hands of Payne, the actors and director Jason Cannon, Constellations is remarkably effective.

We meet Marianne (Hyatt) and Roland (Tipp) as they themselves first meet, at a barbecue. She’s a Cambridge academic studying the cosmos; he’s a beekeeper. But what appears to be ordinary conversation/dialogue quickly develops into a series of quick, sometimes staccato scenes, each announced by a photo flash light and sound. It’s almost like playing one of those interactive games where the storyline can head in different directions based on the player’s actions. Here, the conversation—and their relationship—moves in different ways depending on the response to a question or comment.

In one scenario, perhaps Roland is already in a relationship, or just out of one, or perhaps Marianne is, and their connection might break off. But it starts again, with different outcomes, leading to their becoming a couple, or breaking up, or Roland proposing marriage and being rejected/accepted, and, ultimately, to the gradual realization that Marianne may be suffering from the onset of a disease affecting her speech and more.

As Constellations moves along in all these ways, we experience hesitation, hope, rudeness, evasion, hurt, gentleness, humor, flirtation, fondness, betrayal, joy and grief—all in an evening that runs 75 minutes with no intermission.

That the play succeeds in touching us as deeply as it does is, of course, a credit to the playwright. But it’s also absolutely critical that the two actors, and the director steering them, are simpatico. While we are introduced to some information here about quantum mechanics, string theory and the multiverse (don’t worry, you won’t be tested afterward), so often the impact of the show isn’t about what the characters say, but how they say it. Dialogue is repeated with subtle differences in wording or delivery, and the future is altered. Both Hyatt and Tipp navigate with skill and heart the challenging variations embodied in the play’s concept, and the result is, well, stellar.

Constellations continues through March 16; for tickets call 366-9000 or visit floridastudiotheatre.org.