In the opening pages of Carolyn Parkhurst’s fourth novel, “Harmony,” there’s a line so jarring, so utterly discomfiting that in the hands of another writer it might feel gratuitous. But in Parkhurst’s deft treatment, “Harmony” becomes a story of our time, a compassionate treatise on how society judges parents, how parents judge themselves and how desperation sometimes causes otherwise rational people to choose irrational lives.

(Pamela Dorman Books)

The story begins with 11-year-old Iris in the back seat of the Hammond family car. She’s two days into a road trip with her parents, Alexandra and Josh, and quirky sister, Tilly, headed toward a new life at an off-the-grid camp in the New Hampshire woods. There, they’ll join several other families who also have children with challenges.

You will likely be lulled into believing that you’re being led by Iris, a sweet and typical child whose bothersome older sister is susceptible to vulgar and sometimes violent outbursts. Yes, technically, the girl is narrating, but soon Parkhurst proves she’s in complete control of both the story and her unsuspecting audience. Only six pages in comes that line that casts readers into the angst-ridden lives of the Hammond family. It’s a bold risk with a satisfying payoff.

Over the course of her 13 years, Tilly has been diagnosed with what her mother describes as a series of false starts: obsessive-compulsive disorder; the standard childhood go-to, ADHD; and the rare, slightly controversial and wholly 21st-century disorder, PANDAS. So it’s almost with relief that Alexandra learns Tilly falls somewhere on the autism spectrum, although where, exactly, is unclear.

Her relief doesn’t last long. Even with a starting point, Alexandra discovers that there’s no real path forward, no destination for her brilliant little girl who’s compelled to lick restaurant floors and proposition her father. There may have been lulls, periods in which Alexandra let her guard down enough to believe that the OT, PT and cognitive behavior therapy were benefiting Tilly. She even starts to imagine that her own case of parenting PTSD might abate. But then the most recent in a series of Tilly’s schools calls to say she has become a source of danger to herself and others, and that perhaps she should be home-schooled. Or worse, institutionalized.

Author Carolyn Parkhurst (Nina Subin)

Desperate and out of options, the Hammonds sell off all the comforts of their modern life with its questionable vaccines, processed foods and non­specific toxins in pursuit of hope. Hope manifests itself in the form of Scott Bean, an enigmatic parenting expert who treats children on the autism spectrum with painful observations and tender care. Although not always, as Iris soon discovers and the adults refuse to see.

Certainly, Alexandra was skeptical at first, but modern medicine has let her daughter down a thousand times before, so perhaps modern life is the culprit. Why not believe in Scott Bean when the rest of the world believes Tilly is better off hidden away? Really, autism or not, can’t the parents do something about that girl? Perhaps Scott Bean and his seemingly cultish ways can save her daughter. Perhaps he can save them all.

Told primarily from the points of view of Iris and Alexandra, “Harmony” has a strong plot moved forward by Iris’s keen observations. If the story is largely predictable, it sometimes zags just when you expect it to zig. Yet Iris tells the real story, the one the adults hide from themselves and each other. She sees those who inhabit Camp Harmony for who they really are: flawed beings trying their best to save their families and themselves. She observes their failures with startling insights that can sometimes reveal Parkhurst pulling the strings; channeling an authentic child’s voice is ambitious for anyone. At one point, Iris thinks, “If I’m not a nice girl, then who else can I be? It’s not really a literal question, who else can I be, but for just a second I imagine that it is. I try out Tilly in my head, but she probably wouldn’t even notice there was an awkward situation going on. And then I hear Candy, talking to someone across the field, and it’s like an answer traveling through the air.” These are not the existential musings of an 11-year-old girl.

It’s in Alexandra’s chapters that we find the soul of this novel. Here, Parkhurst cements herself as a writer capable of astonishing humanity and exquisite prose, someone whose wisdom parents and their judges should heed. “ ‘I am,’ you think, and ‘I want.’ And you have no idea how either sentence ends,” may at first appear a simple turn of phrase to conclude a chapter, but it’s all that came before that line, all of Alexandra’s bare truth that demands a moment of self­reflection. Every one of Alexandra’s musings is too brief. Every single one ends with a revelation, a gasp of understanding and universal commiseration.

Perhaps the best part of this novel is the potential in those chapters. They hold the promise for Parkhurst to be truly bold with her next work, to throw off all expectations and conventions, and fully realize what could be her best work yet.

Amy MacKinnon is the author of the novel “Tethered.”

Harmony

By Carolyn Parkhurst

Pamela Dorman/Viking. 278 pp. $26