NEW YORK, NY.- From the outside, you wouldn’t know that Rachel McAdams, the thoughtfully charming star of blockbuster rom-coms, rom-drams, a Marvel franchise and the Oscar-winning “Spotlight,” has been wondering about death.

Maybe it has to do with the therapist who said that her indecisiveness and deep curiosity about seeing through someone else’s eyes, which she’s harbored since childhood, could be chalked up to something called “death anxiety.”

McAdams had long viewed her acting choices as expanding her orbit. “It’s been a way to live a lot of lives in one,” she said. If that was about a fear of dying — well, it didn’t rattle her.

Instead, characteristically, she embraced it. “We don’t have a lot of great coping mechanisms for death in our culture,” she said. “So, yeah, I kind of welcome the opportunity to lean into that — earlier rather than later. Let’s get cozy with it. Let’s get cozy with that next adventure.”

Death hovers like a specter around her latest role, as the single mother of a seriously ill child, in the play “Mary Jane.” McAdams hasn’t done theater since college; she makes her Broadway debut as the title character in this Manhattan Theater Club production, which began previews on Tuesday at the Samuel J. Friedman Theater. It’s by the busy playwright Amy Herzog, who also adapted Broadway’s show of the moment, Ibsen’s “An Enemy of the People.”

“Mary Jane” is the first of her own deceptively spare plays to appear on Broadway, after a celebrated run in 2017 at New York Theater Workshop. Dotted (surprisingly) with laugh lines, it’s about the daily muck and lasting profundity of caregiving, a nitty-gritty subject that’s rarely dramatized. “A heartbreaker for anyone human,” Jesse Green wrote in his New York Times review.

Four other women, playing double parts, round out the cast. The drama revolves around 2-year-old Alex, always offstage, whose condition is signified by the constant attention of a medical staff, and by Mary Jane, a beam of light amid unyielding malady. In a dramaturgical challenge, the antagonist is invisible but all-encompassing: It’s “the American health care system,” said the director, Anne Kauffman.

McAdams, who has a son, 6, and a daughter, 3, with her partner, screenwriter Jamie Linden, had no experience with the fraught universe “Mary Jane” describes, of lengthy stays in the neonatal intensive care unit and vigilant on-hold-forever insurance calls. That’s what drew her, she said.

“I wanted to explore this world and crack this open for myself,” then bring it to the stage. She couldn’t put Herzog’s script down, or get it out of her head. “It was just undeniably powerful, and felt necessary,” she said.

After her career-catapulting back-to-back roles in “The Notebook” and the original “Mean Girls” two decades ago, McAdams, 45, has slowly reoriented her professional life around what feels necessary. Since 2016, that has meant: not very much. Doing one project a year can feel fulfilling, she said, “if you really throw yourself in.”

We met in a midtown Manhattan coffee shop one recent morning before she hustled to rehearsal. In sneakers, a gray fuzzy sweater and a child-made beaded bracelet that read “mama,” with a blond-chestnut mane that she swept around as she talked, she was hiding in plain sight as a mom-on-the-go.

Given her work, she was quick to cry these days, she said. But laughter also came easily, as our conversation circled around having similarly aged kids — McAdams, too, is fluent in reward charts and the fervent belief that our lives will be freer when our children put on their own socks. (“The last frontier,” she said. “Socks.”) Although still private about some details — asked where she lives, she replied, “the South” — she was open about organizing her career so she could be, as she put it, “fully immersed with my kids.”

In Hollywood, taking a step back can mean audience amnesia and producer disinterest — but McAdams braved it before, at the height of her fame in 2005, when she thought things were moving too fast. “I try not to worry about becoming obsolete or irrelevant,” she said, “because I feel like nothing good comes out of fear.”

Even as she has chosen smaller and less showy parts — such as the mother in the 2023 adaptation of Judy Blume’s “Are You There God? It’s Me, Margaret,” her last big-screen role after a stint in the “Doctor Strange” series — McAdams symbolizes the rare combination of superb performer with superstar charisma and down-to-earth bona fides. (Witness last year’s three-episode cameo as herself in the absurdist FXX comedy “Dave.”)

“She has that gear where she can kind of keep going,” said Tom McCarthy, the director and a writer of “Spotlight,” for which McAdams earned an Oscar nomination playing a Boston Globe journalist investigating abuse in the Catholic Church. (The film won best picture in 2016.) Her performance, finely tuned to the habits, and khaki wardrobe, of the real reporter she played, Sacha Pfeiffer, can still deliver a wallop with one look.

Even her emotive listening lands, wordlessly. “She makes that incredibly compelling,” McCarthy said. “Some of that is craft, and some of that is who she is.”

For Herzog and Kauffman, McAdams’ offscreen demeanor propelled her into the role of Mary Jane. “She has a sunniness and a kindness that is so constantly present, and a wryness,” Herzog said. “She embodies so many of the things that I wrote.”

Herzog and her husband, Sam Gold (who directs “An Enemy of the People”), lost a daughter with a rare muscle disorder, nemaline myopathy, in 2023. Herzog said she wrote “Mary Jane” when their child was a few years old, and it reflects some of the specialists who cared for her, in their humor and expansive capacity for problem-solving.

Her hope was to capture not just the medical realities and systemic hurdles of having a critically ailing child — the futility, in other words — but also the joy, determination and faith.

“I think there is a hunger out there for people who have this experience to see it reflected in some ways — and reflected not as a tragedy to be pitied, but as a lived experience with a lot of complexity,” Herzog said.

In rehearsals, experts were called in: a music therapist, a rabbi, a critical care doctor; research that McAdams appreciated. “Normally I have to kind of hustle all that on my own,” she said. (For Season 2 of “True Detective” in 2015, she went on late-night ride-alongs with the Ventura County police.)

The “Mary Jane” cast has found the process therapeutic, and personal. April Matthis, last on Broadway in “The Piano Lesson,” plays a doctor and nurse; her own mother was a labor and delivery nurse, and Matthis recalled the way she upheld her patients’ dignity.

In McAdams, Matthis found a more genuine and giving partner — in real life, a hugger; in character, a “work wife” — than she ever expected. “Like getting in a warm bath, is just how her presence is,” Matthis said.

McAdams grew up a couple of hours outside Toronto, the eldest of three; her mother was a nurse and her father, a mover. By 7, she knew she wanted to act, and once given the reins, succeeded quickly, though she stayed in Toronto, living with her brother or sister, well into her early celebrity.

She retains an essential people-pleasing Canadianness. An acting job lifted her out of college. “I still have nightmares because I didn’t finish my final projects,” she said. “I wake up in cold sweats, like, ‘Oh, I have to play a goddess!’”

Her childhood friends are still her inner circle, said her sister Kayleen McAdams, her makeup artist on “Margaret,” a family job magnified because they were both nursing mothers at the time.

The sisters live on the same street in their small Southern town, where they have conjured what sounds like a takes-a-village utopia. “We’re just so often being like, ‘Hey, I’ll start making lunch, and you run and pick up the kids, and then they’ll all have lunch together, and then, and then, and then,’” Kayleen McAdams said.

Becoming a parent, Rachel McAdams said, made her a better actress: “You just have to be quick on your feet, and completely believe it.”

As we left the coffee shop, a “Mean Girls” fan approached, asking for a photo for his girlfriend (so often for the girlfriend, McAdams noted). She gladly posed, and afterward conjured a whole narrative about the couple. “You always remember who you saw a good movie with, right?” she said.

“The Notebook” is now a Broadway musical, which she expects to bawl through (reading the original script, “I couldn’t stop crying,” she said); “Mean Girls” is a certified juggernaut (a musical, and a movie musical, both hits). That they are still part of the cultural conversation has kept her in fans’ minds, even in the absence of social media and the kitchen table selfies and skin care lines that float other selectively working actresses.

Although her break from the spotlight convinced McAdams that she would be fine if Hollywood stopped calling — returning to teach theater in her hometown “would make my mother very happy” — she views her profession with gravity.

“It’s almost our duty,” she said, “to tell enlightening stories or shine a light on corners of the world that desperately need it,” like the characters in “Mary Jane.” “I also think it’s our job to entertain.” (“Eurovision Song Contest: The Story of Fire Saga,” her last broad comedy, came out early in the pandemic.)

But no matter McAdams’ facility for wringing laughs, “Mary Jane” is sheathed in sadness, and performing it takes a toll. The cast and creators have all dealt with its weight differently.

For Herzog, who lived it, everything changed. “The frameworks I had in place before having a sick kid were a psychoanalysis or a class analysis,” she said, “and neither of those are terribly useful in a situation of anguish.” Her characters turn to spirituality and religion.

Kauffman, who has shepherded the play since its workshops, said it briefly sent her back to temple. Doing the show, she said: “I really understood, for me, what God is. It absolutely comes from the care-taking aspect of this.”

Matthis, too, said she found its portrayal of devotion illuminating. “It’s a real muscular love,” she said. “Part of the reason why I’m so drained is because it’s so moving, and so beautiful.”

McAdams, who takes Buddhist meditation classes, saw in the play the value of community, and of holding space for the unknown. Herzog, she said, is “exploring all kinds of reactions to the things we come up against in life, and doesn’t try to make them all make sense, which I love.”

“To me,” she added, “this play isn’t just about taking care of a child. It’s about taking care of each other.”

This article originally appeared in The New York Times.