The District Theatre's production of Next to Normal may feature the best performance I've ever seen from Sara King, one that even tops her notably angst-ridden, humorous Van's Sister in the former Harrison Hilltop Theatre's Dog Sees God two years ago, and her subtle, hurt, hopeful Lucille in the District Theatre's Parade earlier this year.

Taking on the role of Next to Normal's Diana – the prescription-drug-addled, bipolar woman at the center of this rock musical – King is more understated than she might have been, and more believable for it. Instead of playing this mother, whose mental problems are a major strain on her family, with brassy, crazed theatrics, King's take is more subdued; her Diana appears fearful of her own mind's tricks, trapped by them and oftentimes uncertain of what's real and what's not. King is fantastic in the role, alternately singing softly and belting her way through the songs by lyricist Brian Yorkey and composer Tom Kitt; she doesn't attack the emotion, but is instead enveloped by it, and to great effect. She's especially fine when her character is trying to overcome memory loss, as the look on King's face clearly shows that she's unfamiliar with her surroundings and those around her, but is doing her best to return to her former self and recall her life.

However, there's also something to be said for age-appropriate casting, and as good as King is, director Bryan Tank's production suffers from being performed by actors who are too close in age to be believable as a father, mother, son, and daughter, especially given the audience's close proximity to them in the District Theatre space. I bought each cast member's performance during Friday's show until the lyrics reminded me that these actors, who are probably just a few years apart from each other, are portraying parents and their children. Yet while this is a significant issue, that's fortunately the only major problem I have with the piece.

Tank's take on this story of a woman struggling to overcome her bipolar disorder, and her loved ones' struggles to remain patient with her and keep the family together, matches King's understated performance. While I would describe Next to Normal as a bit heavy-handed, boasting generally real but also somewhat forced emotion, Tank handles it with a realistic approach, avoiding anything over-the-top. (Except, perhaps, for lighting designer Tristan Layne Tapscott's impressively dramatic effects, as when the colors change rapidly when the cast lists drug names and side effects during the “My Psychopharmacologist & I” number.)

Kelly Lohrenz wears angst well as Diana's daughter Natalie, a teen who feels neglected by her mother, turns to Mozart to escape her crazed life, and, in a subplot, is wooed by an ever-patient classmate, endearingly played by Michael Ross Tallon. As Diana's son Gabe, Tapscott is fine, but seems a touch forced; the actor appears to be trying too hard not to fall short of the character's poignancy. Steven Lasiter's performance as Dan feels a bit soft for a man who's lived with his wife's mental difficulties for almost two decades, though it could also be argued that Lasiter's gentle spirit is appropriate for a long-suffering husband. And while portraying two different doctors attempting to treat Diana's disorder, James Fairchild sings well and seems human, occasionally displaying a somewhat unprofessional frustration while his characters are trying to come up with solutions to the woman's disorders.

Tapscott's set design is more sprawling than is typical for a District Theatre production, with two stories of usable walk space and an attic crawl space on a third level, plus a staircase rising to the second floor and a ladder climbing to the third. Painted almost completely in black, the walls also include black-and-white pictures of the family, with the full images spread across several separate sheets of paper, symbolizing the family's brokenness.

It's apparent that those involved with the District Theatre's production have a deep respect for the material and are passionate about presenting it. Those feelings may have blinded them, during the casting process, in terms of considering the actors' ages, but while this age incongruity does hurt the piece, it doesn't hurt it so much as to render the show unwatchable. The material is so good, so interesting, and so different from typical Broadway fare that Next to Normal shouldn't be missed. Thankfully, Tank's treatment of it shouldn't be, either.

Next to Normal runs at the District Theatre (1611 Second Avenue, Rock Island) through September 8, and information and tickets are available by visiting DistrictTheatre.com.