In Threshold, her play in progress, writer and actress Amy Brenneman describes the experience of giving birth to her daughter, Charlotte, and the spark of recognition that followed.

“Amid the din and the excitement of the delivery room I had this surprisingly clear thought,” she says. “Oh, it’s you. I didn’t know it was going to be you. This time around, I’ll be the mom.”

On Tuesday afternoon, she delivered the line standing barefoot in the middle of the Patricia Nanon theatre at the Yard surrounded by a different kind of din and excitement. Yard dancers Jesse Keller Jason and Alison Manning knelt behind her. Director Sabrina Peck stood just off stage. Sound designer David Van Tieghem finished his lunch as he managed cues from a folding table. Stage manager Luana DeBorst took notes on her laptop. Fellow performers Cate Woodruff and Nell Geisslinger waited offstage.

Amy Brenneman works on a new play at The Yard with director Sabrina Peck. — Ray Ewing

Ms. Brenneman’s daughter Charlotte, now 18 years old, watched from her seat on the risers, leaning against a stack of folded stage curtains. She listened as her mother described her honesty, her gut instincts, her “animal heart.”

As part of the Yard’s Offshore Creation residency, the group has spent two weeks workshopping Threshold. A version of the play, Threshold 90-52-15, debuted at the Yard in 2016 but has evolved in the years since. Threshold 90-52-15 focused on Ms. Brenneman’s relationships with her 90-year-old mother and 15-year-old daughter (the numbers in the title represented their ages at the time), this version has been stripped down to focus on Ms. Brenneman’s experience of motherhood.

The play is about raising Charlotte, who has a rare chromosomal abnormality that was not diagnosed until she was 15. In the play, Ms. Brenneman grapples with the values and beliefs that are the bedrock of what she calls dominant culture: work hard and you can achieve anything, you too can eventually fit in.

“My daughter is not on the autism spectrum, but she’s always in the clump: ‘Autism and Related Disorders,’” Ms. Brenneman said. She said the realization that drives the play is that the problem is not Charlotte’s difference, it’s the notion that difference is something to be corrected.

Ray Ewing

“There’s an incredibly new and different way of looking at these differences. . . .They’re part of the diversity of humanity and always have been,” she said.

At rehearsal, sound designer David Van Tieghem read the dominant culture lines in a coaxing voice from the folding table. “You can do this. Charlotte can do this, she just has to work a little harder than some kids. But with a little can-do spirit, she’ll catch up and fit right in,” he said.

Ms. Peck stopped the scene and asked for a drumbeat under the dominant culture lines. Mr. Van Tieghem cued one up. The dancers began a regimental combination.

Ms. Peck said incorporating movement to enhance a story is a frequent practice for her.

“I really enjoy setting an intensely personal story in a context of those heightened theatrical elements like lighting, sound, music, visuals and movement,” Ms. Peck said.

Ms. Peck and Ms. Brenneman met while studying at Harvard and have collaborated on three theatre pieces since, including a play called Mouth Wide Open about Ms. Brenneman’s struggle with chronic illness, and Threshold 90-52-15.

“What Sabrina and I do has a lot of what I would consider a collage,” Ms. Brenneman said. “We have to get it up on its feet. It’s not a play-reading in the traditional sense because the words are only one element of it. We have the opportunity in a safe way to get it up on its feet.”

The two-week residency is geared entirely toward the creative process. The play will not be performed publicly at the residency’s close.

“We have never ever had the opportunity to explore work without a paying audience at the end of two weeks. I keep pinching myself,” Ms. Brenneman said.

Tuesday afternoon at rehearsal, Charlotte stepped on stage to practice the final scene, taking her mother’s hand. Earlier, Ms. Brenneman described reuniting with her daughter recently on the Island. It sounded like a similar feeling to when the two first met in the delivery room 18 years ago, a spark of recognition.

“We’ve been talking about this character Charlotte and then when she arrived on the ferry, I was like, Oh, hi.”