Changing the rules, 'Theresa' then strays

What's the difference between a theatrical device and a gimmick? The simplest answer might be that a device is a gimmick that works. It draws attention to the play, not to itself; it serves the characters, story, and themes, instead of distracting from them.

Sadly, what Janet Kenney has devised in "Theresa at Home," her new comedy about a perplexed former nun turned newlywed, is a gimmick. The play deploys three actresses in multiple roles, but the trick is that (until very late in a long evening) only one of them speaks in each scene. Sometimes the speaker is alone onstage, addressing an invisible companion; sometimes the actress playing the listener is standing right there, but she neither appears to hear nor responds aloud -- even though the speaker then "responds" to her unspoken lines.

The technique seems like a misguided cousin of the one-woman show, and, indeed, Kenney has said that that's how this play began in her mind. If this variation were to work, however, she'd need to make clearer rules for the game she's playing: Why do the characters not speak normally to each other, why do the silent characters sometimes stay and sometimes leave, what is the relationship between characters when they're both onstage but only one is fully present, and when (if ever) does it make thematic sense to switch the rules and have them start interacting?

Even if all those questions were answered, the play would still be dangerously close to a theater game rather than a fully fledged comedy. But Kenney seems to see a link between her device and her themes -- something about how we mishear or fail to hear the people we love, though that's a guess more than a deduction from what's onstage -- and so honing the device might also bring the themes into sharper relief.

As it is, "Theresa at Home" takes more than two hours to explore some pretty familiar territory. We're in Boston, in 1956, and Theresa has left the novitiate to get married. But she's a good Catholic girl in a play, so naturally she's frightened and disturbed by sex -- something she's remarkably willing to discuss with the assorted visitors who pop in while she's unwrapping her wedding gifts and praying to the Blessed Virgin.

Theresa's guests include her mother, two of her sisters, her grandmother, an upstairs neighbor, the Mother Superior from her old convent, and a couple of Welcome Wagon ladies. Kenney has a fine eye for character and a fine ear for comedy, so these women are both touching and funny. But, especially in their longer monologues -- as when the nun uses a turkey baster, two kiwis, and an egg to explain the facts of life, the neighbor discusses her weight-lifting prowess, or one sister launches into comic rhapsodies about her plans to move to Africa with her boyfriend -- they can start to feel like freestanding showcases for comic acting, rather than dramatic characters.

The Village Theatre Project and Boston Playwrights' Theatre have assembled three skilled performers here; Stacy Fischer, Julie Jirousek, and Cheryl McMahon invest all their characters with distinctive personalities, quirks, and real warmth. Jon Savage contributes an appropriately real/surreal set, Mary Grusak's costumes are at once simple and ingenious, and Haddon Givens Kime has managed to write a recurring tune that embraces everything from '50s doo-wop to African drums to "Ave Maria."

All this caring work, along with Kenney's own humanity and humor, makes you long to embrace the play. Unfortunately, though, its own awkward device keeps getting in the way.

Louise Kennedy can be reached at kennedy@globe.com.