Playwright Rebecca Gilman, 49, doesn't shy away from vivid, intensely troubling explorations of broken people living on fringe of society. Roughly a decade in gestation, Luna Gale—Gilman's seventh collaboration with the Goodman Theatre—relentlessly delves the plight of children caught in Iowa’s frighteningly dysfunctional social services system.

Chicago caught up with Gilman just after Luna Gale's opening and spoke with the long-time Andersonville resident about her inspiration for the harrowing drama, her long-term artistic relationship with the Goodman artistic director Robert Falls, and what book she's reading next.

Luna Gale opens in an ER where a tweaked out meth addict is trying to force feed Skittles to her passed out partner. This is almost a replication of something you actually saw, right?

It is. I sprained an ankle hiking in Eugene, Oregon. We went to the ER where there were actually three meth addicts, including one who was eating cheesecake voraciously and a guy with band-aids on all his fingers. I'd read enough about meth to know how it makes people behave. One of the things is that, in addition to sugar cravings, you start feeling like you've got bugs living under your skin. So you try and pick all the skin off your fingers to get the bugs out.

The girl in the ER with the cheesecake was on the phone with what was pretty clearly her drug dealer. Then she got another call where she started giving all kinds of instructions about what time the babies should go to bed, when they should be fed, what they liked to eat—she was so concerned and specific about her children. I started thinking, huh, maybe she's a really good mother.

You also drew inspiration from a Frontline documentary about a little girl who was murdered by her adoptive mother, who was a social worker. Why did you think it was also an important story to dramatize?

I think you can really judge how well a society functions by how its most vulnerable members are treated. If we can't take care of our children, we are failing. We're not doing our job. I'm totally paraphrasing Dostoyevsky who said, you can judge a society by its prisons. You can also judge it by its children.

The Glory of Living, about a 15-year-old who becomes a serial killer, also deals with issues of bad parenting. Why the return to this?

I keep coming back the fact that there's this vast inequality in our country, not everyone gets an equal opportunity from birth. Whenever I see people whose lives have been shut down early because they simply weren't given the basic tools to succeed, I think that's kind of criminal. Luna Gale does go back to some of the things I tried to explore in The Glory of Living. I guess I just don't see us getting any better in a lot of respects.

Why did you Luna Gale in Iowa?

I lived in Iowa for a long time. I've also lived in the Midwest for a long time and I've seen how we can be completely overlooked. So many narratives are set in big cities among people of privilege. It's important to tell the stories of people in places that don't get written about so much.

You’re working with Chicago actress Mary Beth Fisher for the third time. Did you write Caroline, the burnt-out social worker in Luna Gale, with Fisher in mind?

It took me like nine or 10 years to figure out [what the plot would be]. When I saw the kids in the ER, that's when the plot finally kicked in. But even at the beginning, before I had a plot, I really, really, really wanted to work with Mary Beth again. She totally gets my language and my sense of humor.

What about Robert Falls? What makes the partnership work so well?

Bob hears my plays so clearly. He makes them fully realized and more. But the 'and more' is never that he imposes some crazy directorial vision on them. He never imposes on the text but he finds ways to enrich and heighten it. I feel like we challenge each other to do our best work. And we're at a point in our relationship where we feel free to challenge each other pretty bluntly.

What are you working on now?

I've got a play opening at the Repertory Theatre of St. Louis in March, called Soups, Stews and Casseroles, 1976. It's about a man in Monroe, Wisconsin, who works for the factory and how things change after the factory is bought out by a union-busting major manufacturing conglomerate.

So what do you do when you're not hiking or writing?

Well, I'm in this book group. We're doing Saul Bellow's Herzog next and I haven't even read it. I'm totally unprepared.

Through Feb. 23, at the Goodman Theatre, 170 N Dearborn.; $25–$81.