Playwright Rebecca Gilman is known for tackling the topical (racism in academia in "Spinning into Butter," stalking in "Boy Gets Girl") and for carefully, even over-bluntly, placing her characters into discomfiting moral thickets. In "Luna Gale," premiering at Chicago's Goodman Theater, she crafts what is unquestionably her sharpest play yet, a layered and wholly involving tale of an achingly well-meaning social worker who makes arguably bad choices largely because there aren't any good ones. Play has a promising future: In addition to potential ubiquity on regional stages as well as a Gotham run, "Luna Gale" also represents the most film-friendly of Gilman's works.

The title refers to the baby of two young meth addicts, Karlie (Reyna de Courcy) and Peter (Colin Sphar), whom we meet in the waiting room of a hospital where they've brought the sick Luna Gale. Karlie is ultra-hyper; Peter is passed out. It takes the experienced social worker Caroline (Mary Beth Fisher) only seconds to determine she needs to take their kid away from them. And, in what seems a fortunate circumstance, Caroline places Luna Gale with Karlie's mother Cindy (Jordan Baker), which avoids the potentially calamitous crapshoot of foster care.

But Caroline quickly discovers that even the obvious choice comes with complications. Karlie, played very effectively by de Courcy with an over-intensity that makes her extra vulnerable, is furious, not wanting her daughter to be raised with the same smothering fundamentalism she resisted. And her fears are soon borne out, as Cindy wants to make up for failing to convince Karlie of the righteous religious path by raising Luna on the same path, and immediately asks to start the process for permanent custody. Caroline is befuddled by the choice. After all, she knows hopelessness when she does -- and doesn't -- see it. All the young Karlie and Peter need is the right rehab; too bad there's a long waiting list but, you know, budget cuts.

Caroline, played by Mary Beth Fisher with quirky intelligence and just the right balance of expertise and exhaustion that comes from decades of emotionally draining work, navigates not just bureaucracy but a condescending boss (Erik Hellman, who nails the character's oh-so-irritating smugness), a predecessor's past mistakes that deprive her of accustomed autonomy, accusations of religious bias, memories of her own past that the case brings to light, and another young client (Melissa DuPrey) whom the system has served well but still might not be able to save.

Bureaucracy may be frustrating, but here it's actually Gilman's friend. Even while the playwright exposes layers of complexity, the story drives forward with clear process points -- visits, court appearances -- which provide the type of firm but unforced plot structure that the playwright has struggled to create in the past. Gilman makes bureaucratic in-fighting genuinely entertaining, if not comforting, as we watch the characters scramble for advantage, always convinced they're doing iffy things for the right reasons. The constant forward movement, the power plays, Gilman's mature wit and the fact that Luna Gale remains as yet undamaged and therefore a figure of hope, all keep the piece from getting mired in the darker aspects of the tale.

Director Robert Falls understands the complex tone here and leads a terrific, carefully selected cast in finding humor and possibility in hard situations. Even Todd Rosenthal's revolving set shows us a set of subtly unremarkable environments, the type of clean places where messy human things happen. "Luna Gale" presents a nearly flawless depiction of a world where flawed people make flawed decisions in a flawed system, and there's still a chance things will work out.

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