Details are sparse in Shayan Lotfi’s play “What Became of Us,” but the imprecision is by design. Onstage at Atlantic Stage 2 in Manhattan, the two-hander is meant to be one size fits all, to a degree: a story of immigration that doesn’t specify its characters’ country — neither the one they quit, in the Global South, nor the one they adopt, in the Global North.

Q (Rosalind Chao), the daughter of the family, is alone onstage when she begins mining her memories of what she will always call “the Old Country,” from which she emigrated with her parents when she was 6.

“They wanted to leave because of the economic, and the political,” she says, her vagueness allowing space for imagination. “They wanted to leave to find autonomy, and safety.”

And, she suggests, they wanted their then-only child not to be frightened by the momentous change they had decided on: “They explained the journey to me using words from the fantastical stories I loved to read: adventure, new, exciting.”

Q’s gaze hovers above the audience, but she is not talking to us. These recollections are for Z (BD Wong), her sibling, who was born in what she calls “This Country,” when Q was 7. For all of them, the new baby would be “a root into This Country that could never be ripped out.”

Does it need mentioning that there is nothing sinister in that sentiment — that their parents were simply building their family as they built a new life in a new place, to which they wanted to be connected? Such are the electrified politics around immigration these days, and not just in the United States, that maybe it does.

Those politics make “What Became of Us” a highly topical play, if a frustrating one in Jennifer Chang’s production for Atlantic Theater Company. When I saw it two weeks into previews, I wished I had waited another week, because Chao and Wong hadn’t yet settled into their roles. For much of the play, the words they spoke were still just words; the breath of life wasn’t in them yet.

Instead, the performance had a lulling quality. That’s a hazard of a script filled with straightforward, declarative sentences, some of which lapse into cliché. It’s also an obstacle to letting the strong lines really pop.

The play traces Q and Z’s lives from childhood into old age: the elder sibling forever a product of two cultures, with an understanding of their parents that comes from having known them first in the nation they were born into, then in the one that humbled them; the younger sibling a rebellious, irreverent, go-getter native of the new country, embarrassed by their parents’ outsiderness, bewildered by Q’s self-sacrificing devotion to them.

Almost never do Q and Z look at each other as they speak their memories. That may be emblematic of the disconnection that troubles their relationship, but it brings an unhelpful air of detachment to the whole enterprise.

Lotfi has constructed the play so that Q and Z can share any diasporic background from any part of the Global South, which includes much of Asia, Africa and Latin America. Chao and Wong perform through June 15; a second cast, with Shohreh Aghdashloo as Q and Tony Shalhoub as Z, performs June 10-29.

Watching the play, knowing that, it was hard not to envision the production feeling significantly different in the hands of other actors, if they are able to slip into the skin of Q, who grows up to be a librarian, and Z, who grows up to be a chef.

Common human dynamics are at the heart of Lotfi’s experiment, but it has no emotional weight if the characters feel like constructs rather than individuals. With so much particularity deliberately left out of the play as written, it needs its actors to bring those qualities. Therein lies universality.

What Became of Us
Through June 29 at Atlantic Stage 2, Manhattan; atlantictheater.org. Running time: 1 hour 15 minutes.