“Bitter” may be the adjective in the title of “This Bitter Earth” at Penumbra Theatre, but a better description of the play would be “generous.”

There’s a generosity of spirit in Harrison David Rivers’ witty drama, which shifts back and forth in time to illuminate the relationship between two strikingly different men. The play is also generous in how it unfolds, its two characters keeping secrets from us in a way that comes across not as withholding but as a means of giving us the space to try to understand their complexity. And there’s generosity in the conclusion of “This Bitter Earth,” which strives to find meaning in tragedy.

Beginning in St. Paul in 2015, “This Bitter Earth” skips around in time, peeking in on crucial moments in the romance of Jesse and Neil that began in New York in 2012. Jesse is black and Neil is white but, while race is an issue in their relationship, it is not the issue.

The men are very different — neurotic Jesse uses sarcasm to protect himself, whereas Neil is open and easier to read, to the point of being a little too good to be true. While Jesse pours his passion into his work as a playwright, Neil’s passion is for social justice causes, including Black Lives Matter, that Jesse has little time for.

“This Bitter Earth” may sound like the sort of smart, two-character, one-set play that theaters around the country clamor for, in part because they’re not expensive to produce, but Talvin Wilks’ direction reveals that the play’s seeming simplicity is deceptive. Yes, it all takes place in Maruti Evans’ handsome take on a vintage, tin-ceilinged condo, but the all-white set that greets theatergoers as they settle into their seats is an early clue that “This Bitter Earth” aims for something beyond realism.

The set will represent a variety of places and time frames and the white backdrop frequently becomes a screen for projections that overtake the play, depicting key moments in the Black Lives Matter movement one moment, cluing us to time shifts the next and suggesting the William Morris wallpaper-like backdrop of a painting by acclaimed Barack Obama portraitist Kehinde Wiley the next. The set, in other words, is as fluid and mysterious as the relationship it helps to define.

That relationship is slightly off balance, in part because Jon-Michael Reese is flat-out spectacular as Jesse. Reese delivers Rivers’ rhythmic barbs with aplomb. (When Neil says, “You’re twisting my words,” Jesse counters, “This is a fight. We are fighting. Of course I’m twisting your words.”) But Jesse is no I-laugh-to-keep-from-crying cliché because Reese smoothly finesses the play’s tricky shifts of scene and mood. Kevin Fanshaw is great at Neil’s heated speeches, especially when he recites an Essex Hemphill poem at a BLM rally, but he falters in Neil’s playful, intimate moments.

“This Bitter Earth” caps off a crazy three months for St. Paul playwright Rivers, whose work as been produced by three local companies in that time, in addition to a reading of a fourth at Playwrights’ Center. “Bitter” showcases his gift for exploring compelling ideas with humanity and humor, as in a scene in which Jesse asks Neil if it’s his first time with a man of color. It also feels like a tantalizing promise of many good plays to come.