The word “love” appears more than 60 times in the text for Sarah Ruhl’s new play tracing her intense relationship, while teaching an undergraduate class at Yale, with a student named Max Ritvo. Don’t get the wrong idea: Ms. Ruhl was a happily married woman when she met Ritvo, who died in 2016 after a long battle with cancer, and their bond was not a romantic one — at least not in the sense that word is generally applied to couples.

There is, nonetheless, a heady seduction occurring in “Letters from Max, a ritual,” based on a book Ms. Ruhl wrote with Ritvo and published after his death. It’s forged, as some more conventional seductions have been, through poetry. Max, who is played at alternate performances by Ben Edelman and Zane Pais, is a dizzyingly precocious writer of verse; watching Sarah, played by the radiantly expressive Jessica Hecht, react to them, you might even be reminded of Cyrano’s Roxane, rapt as she listens to another man deliver the true poet’s words.  

Max is more forthright in his appeal to Sarah’s mind and soul. The “student who becomes a teacher” and the “teacher who becomes a student,” as Ms. Ruhl identifies them in her character listings — a duality that is reinforced throughout the play — are on the surface a study in contrasts. The soft-spoken Sarah repeatedly references her Midwestern, Catholic background, in which demonstrations of love were, as she muses at one point, “subtle.”

In contrast, Max is a person who lives out loud. “I love the sound of my own voice,” he admits, and in Ms. Ruhl’s portrait — heavily informed by Ritvo’s own writing — this quality becomes not only endearing but inspiring. The playwright has always had a gift for fusing the whimsical and the cerebral, and in Ritvo, she clearly found the perfect muse: a prodigy who can summon equal enthusiasm for Rumi and Cyndi Lauper, and whose zest for living, and for other people, seems to burst out of his failing body.

At the preview I attended, Mr. Edelman’s muscular but nuanced performance, which could be as bitingly funny as it was heartrending, made all of this palpable. Mr. Pais lent sensitive support in a few small, silent roles, and played pensive original music — created by Mr. Pais with sound designer Sinan Refik Zafar — on guitar. (When Mr. Pais plays Max, Mr. Edelman plays his own compositions, also crafted with Mr. Zafar, on piano.)

Director Kate Whoriskey guides the cast with characteristic compassion and wit, culling an especially thoughtful, beguiling performance from Ms. Hecht, who has made something of a specialty of women characters whose charming quirks can belie their depths. Sarah’s depth is hardly in question, but the actress mines the humor and poignance in her timidity and self-doubt; after she begins to share her own, long-hidden poems with Max, and he responds with gushing praise, Sarah quips that perhaps she’ll develop “the courage to send them out one day. Or, God forbid, read them aloud in public.”

The most moving passages in “Letters From Max,” not surprisingly, are those that find the players reciting Ritvo’s poems and written exchanges with Ms. Ruhl, whose own flair for hauntingly lyrical expression is very much in evidence. Some more conversational dialogue can threaten to veer into the hifalutin; observing Sarah’s love for soup, Max suggests it’s “the food that most allows your mouth to approximate silence. Chewing is so very similar to speech.” Sure, but can’t a shy artist and academic just like the taste of soup?

At its glowing best, this play blasts down the notion that a life of intellectual curiosity need be a dispassionate or lonely one. For anyone who may believe as much, the character of Max will be a revelation. Ms. Ruhl has surely always known better, but Ritvo seems to have reaffirmed her belief in the power and beauty of both friendship and language. 

Writing to Max as his condition deteriorates, Sarah assures him, “I do not believe you are only carrying a torch of fear into the night with you. What I see you holding is a torch of bravery, and generosity to all of those around you, and heart.” With “Letters From Max,” Ms. Ruhl keeps that torch burning, as both a testament to their love and an example for all of us.