I celebrate myself, and sing myself,/ And what I assume you shall assume, /For every atom belonging to me as good belongs to you.

— Walt Whitman, from “Leaves of Grass”

Haunting.

It shouldn’t be this way.

Invisible Theatre’s production of Lauren Gunderson’s two-character, 80-minute long “I and You” features a couple of teens whose chief forms of communication are text, tweet, and Facebook pages.

They should be insufferable.

But no, they haunt. As does this small play with big ideas directed with a knowing hand by Glen Coffman.

The play ripples long after you’ve left the theater. The story haunts, Gunderson’s construction haunts, and the performances haunt.

The plot centers on Caroline and Anthony, two high school classmates who must work on a joint project about Walt Whitman’s “Leaves of Grass.”

She is confined to her room most of the time, weak and waiting for an organ transplant.

He has trudged Whitman’s poem and poster board up to her room to finish the project, due the next day.

Gunderson’s dialogue perfectly captures the awkwardness, the defensive cynicism, the insecurity of youth and juxtaposes those against Whitman’s elegant language and profound ideas.

And the playwright has created a couple of characters that never struggle to be cute or clever. We buy into this story because of who they are — she is prickly, funny, given to outrageous abandon one moment, and pulling blankets over her head to hide her embarrassment the next.

He is smart, a tad gawky, about as uncomfortable in her company as she is in his. And he really, really wants to get this project done.

The two actors playing Caroline and Anthony charm us, humor us, and completely pull us into their world.

Lucille Petty possessed Caroline — or maybe it was the other way around. Every move she made, every word, was so steeped in the natural swagger and shyness of a teenage girl that it was easy to forget you were watching a play.

And Nick Trice possessed his role, as well. His Anthony was a genuinely nice guy who feels a bit geeky standing in this girl’s room trying to digest Whitman. We ache for him and cheer for him.

These actors have been on several Tucson stages. They almost always are quite good, but this may be their best work here.

Gunderson’s characters discuss death, sex, connections to each other and the universe — all ideas provoked by Whitman’s poem — but it all feels wonderfully organic.

There’s a surprise ending that somehow made perfect sense, and underscores Whitman’s ideas.

And, especially, haunts us.