There is a world for those on the autism spectrum, a world that belongs to them and occasionally, and sometimes without reason, intersects with the world that belongs to the rest of us.

That private and perplexing world is told in "Mockingbird," what may well be the most powerful play I’ve ever seen staged by First Stage, a company that has an enviable record of powerful theatrical events.

The power of this play is in the script, but also in the hands of two women, one an 18-year-old actor and the other a director, Marcella Kearns, who has staged a sensitive and creative portrait of a girl, her world and the circles that surround her.

Alex Salter, a senior at Germantown High School, plays Caitlin (in the eagle cast), a young girl with autism. The autism spectrum is a wide one, and it’s often difficult to determine what spot on that spectrum belongs to a child.

Caitlin has many of the obsessive, repetitive characteristics of that put her on the spectrum. Her place of comfort is on her couch, with a pillow over her head, her purple sweater available to be chewed on, a plush blanket to wrap herself in and a dictionary that she reads religiously, learning words one on top of another.

Caitlin’s brother, Devlin, has been killed in a school shooting, and his death, following the death of her mother, has driven Caitlin into a place that belongs only to her and that she is sharing with her departed brother. That sharing is a disillusioning mystery to her father (Dan Katula) who is torn by his own grief for his son.

Caitlin’s world is filled with well-meaning adults who want to help her deal with her particular brand of grief.

Asked by a counselor (Marvette Knight) how she is feeling, Caitlin replies that she "feels like Tivo, fast forwarding past the bad parts." She is told, over and over, to look at people when she talks to them. She suffers a TRM (Tantrum Rage Meltdown) in her counselor’s office.

Her behavior is strikingly and hauntingly familiar to anyone who has spent time with an autistic child. My great nephew Jackson is autistic, and he’s a loving and delightful child but there are those unexpected moments when his own private world erupts into something that catches everyone by surprise.

Kearns has given Salter plenty of room to dig deep into this girl who we might wonder about but who seems to have her own certainty of her place in the world. She is bedeviled by noise and by those who want to touch her, by those who want to make her interact with others and, perhaps most of all, by a wooden crate that Devin had been building, a crate that sits unfinished.

That crate is a vivid and constant symbol of a place in the world where Caitlin can feel, if not safe, at least cloistered from the chaos of the world. It is chaos that is at the heart of all that triggers the sometimes savant-like moments in Caitlin’s life.

It’s difficult to describe the incredible performance Salter gives in this demanding role. She has a wrap on the overt and obvious but also is warmed with the nuances of Caitlin. She finds the loneliness of Caitlin but also finds the humor and the moments of both joy and sorrow as well as the confidence and doubt that so mark the life of this young girl.

Headed off to college, we can only hope that she comes back to Milwaukee to continue making her mark in the world of theater.

Kearns proves, again, with this production that she is a double threat when given a script and a stage. She is a fine and versatile actor with a special penchant for comedy. And with this performance, she shows that she can take a subject like autism and craft a story woven with truth and honesty.

This is an important play that every family ought to go see.

"Mockingbird" runs through April 9 and information on tickets and showtimes is available here.

Production credits: Director, Marcella Kearns; Costume Designer, Lyndsey Kuhlmann; Scenic Designer, Brandon Kirkham; Lighting Designer, Jesse Klug; Sound Designer, Sarah N. Ramos; Young Performer Coach, Brenna Kempf; Stage Manager, Marissa Ashlyn; Assistant Stage Manager, Jake Schertz.