‘Mary Jane’ review: Rachel McAdams is a strong mom in teary Broadway play

Rachel McAdams brings an instantly heartbreaking quality to her performance in “Mary Jane”: Her steadfast optimism.

Writer Amy Herzog’s affecting play, which opened Tuesday night on Broadway at the Samuel J. Friedman Theatre, is about a single mother whose 2-year-old son Alex is chronically ill. 

The poor kid, who the audience never fully sees, spends most of the drama in another room in bed, attached to monitors and oxygen tanks that beep and hiss. At this point in his young life, he can’t even control his head yet.

His mom Mary Jane’s (McAdams) entire existence, with nary a break to relax, revolves around the boy’s care. Nurses, friends and her superintendent stop by to talk and support her. And they help, of course, but they don’t change the hard reality of the situation. Unlike Mary Jane, they have lives on the other side of the door.

One of the woman’s many sad-but-clear-eyed observations is that she has become accustomed to hardly ever sleeping in her tiny New York apartment. “I used to be someone who treasured sleep,” she tells a nurse named Ruthie (Brenda Wehle). “Cherished it.”

Now, she can barely remember the sensation.

The depth that McAdams gives Mary Jane, in the most natural way, is her positivity. In the film “The Notebook,” in the TV series “Slings & Arrows” and even as the Plastic villain in the movie “Mean Girls,” the actress has always had a je ne sais quoi that goes beyond openness and vulnerability. She emanates a light from within.

And when it shines, not on a romance or teen comedy, but a relatable mother’s helplessness, we’re shattered.

Compassionately told by Herzog, the play is a tough story about a struggling single parent of limited means muddling through one day at a time. The show, I’ll admit, takes more than one day to fully sink in.

“Mary Jane” is not a vehicle for showboating, or some explosive Mom vs. Society battle, and rightly so. Herzog’s drama is calm, and made up of slice-of-life conversations familiar to anybody who’s been a caretaker or knows one. 

And at times, I found director Anne Kauffman’s production too quiet for the Friedman, intimate though the venue is. Even a simmering show needs to build, and the middle of “Mary Jane” leans static.

But the play achieves a devastating serenity in the end when we leave the apartment and, in a scenically impressive transition from designer Lael Jellinek, move to the pediatric intensive care unit of a hospital, or PICU.

While Alex is in surgery, Mary Jane speaks to a comforting Buddhist chaplain named Tenkei, played by Wehle in a turn as stunningly transformational as the set. 

Tenkei asks Mary Jane to describe her son — I tear up just thinking about it — and as the frightened mother talks about his stubbornness, his love of animals and his smile, the stage’s brightness dims.

But McAdams’ light doesn’t.