At Juilliard, he met Mr. Gold, at the time a directing student. Mr. Gold was immediately struck by Mr. Isaac’s “easy energy and an easy relationship to his talent and having an incredible amount of talent” and a shared belief that “acting shouldn’t look hard,” Mr. Gold said.

The two of them fooled around with some comic scenes from “Hamlet,” making a pact to work together one day on the whole play. They both got “bit by it and obsessed by it,” Mr. Gold said, speaking by phone. Those talks continued, and two years ago, Mr. Isaac signed on, saying he felt he had to do it “before the knees give out.”

“You can only be so old and be upset that your mom remarried,” he said.

Once he’d agreed, Mr. Isaac began reading academic books, watching famous past performances, playing a recording of John Gielgud’s Hamlet “and just listening to the beauty of that man’s voice,” he said. After creative tensions with the production’s original home, Theater for a New Audience, “Hamlet” shifted to the Public Theater, where Mr. Isaac had made his post-Juilliard debut, and dates were set.

But then his mother got sick and his partner, the documentary filmmaker Elvira Lind, got pregnant, and suddenly “there were a lot of things that really connected on a very personal level,” he said. As Mr. Isaac explained, performing has always helped him come to terms with his emotions. “This is how I’m able to function,” he said. “The only way that I’m really able to process stuff is through reflecting it.”

Some of the visual language that he and Mr. Gold settled on — the syringes, the IVs, the PICC lines — make his memories and associations even more visceral. His Hamlet wears rumpled clothes and has a 5 o’clock shadow (if you’ve seen Mr. Isaac’s movies, you know his facial hair is a key to character) to approximate “the look and feel of spending long hours visiting a loved one at the hospital,” he said.