“He made some remark about the dead.”

The man who makes the remark, on the first page of Emma Donoghue’s engrossing novel, is the driver of an uncomfortable horse-drawn wagon called a “jaunting car.” The woman to whom he directs it is Elizabeth (Lib) Wright, a nurse trained by Florence Nightingale, and proud of it. She’s been hired by a committee of influential locals to spend two weeks observing a young girl named Anna O’Donnell.

When Lib asks her driver for clarification, he tells her they are in the exact dead center of Ireland, and even before she reaches the tiny village where she will lodge in a room at the spirit grocery (a store selling alcohol), Lib becomes aware that the Irish Midlands are dead in ways that go beyond geography. She glimpses “a woman in a filthy frilled cap ... stationed on the verge, a knot of children in the hedge behind her.” The woman’s cupped hands are lifted to the sky, as if to catch heavenly manna. “‘The hungry season,’ muttered the driver.”

The Irish potato famine has been over for seven years when The Wonder commences (in 1859, by my reckoning), but the aftereffects are everywhere. Lib herself is given plenty to eat, but very little of it appeals to her English palate. She often loses her appetite, and after a particularly nasty meal of cold griddle cakes, she wonders - with some justification - “Did the Irish hate food?”

Food is the dominant chord that runs through “The Wonder,” because the girl Lib has been hired to observe - along with a mostly silent nun named Sister Michael - is said to have taken none at all since her 11th birthday, four months previous. Yet she is supposedly healthy and vital, a true wonder child in a century famous for its wonders (many of which, like the Cardiff Giant and the Davenport Tablets, later proved hoaxes). Lib and Sister Michael’s job is to watch the girl day and night, in eight-hour shifts, to make sure no one is slipping her chow on the sly.

In an author’s note, Donoghue says that The Wonder was inspired by almost 50 cases of “so-called Fasting Girls” between the 16th and 20th centuries, but the case that most closely resembles the one in her novel is that of Sarah Jacob, a Welsh child of 12 who was said to have gone without food for more than two years. After her story was reported, a team of nurses was hired to keep watch and discover if the girl really was fasting. This close observation began on the 9th of December, 1869. Sarah Jacob died of starvation a week later. The following year, her parents were tried for manslaughter, convicted and sent to ­prison.

The village committee paying Lib’s salary has a rooting interest in proving Anna O’Donnell to be the miracle her family purports her to be. They see lots of tourist cash pouring into the community, of course, but the religious implications seem even more important to these ­devout Roman Catholics. “Couldn’t this little girl be Ireland’s first saint canonized since the 13th century?” one committee member rhapsodizes as Anna - yellow with jaundice, swelling with dropsy, unable to make urine, suffering from incipient pneumonia - lies dying before their eyes.

Lib begins her increasingly excruciating duties in the rickety O’Donnell home believing that the entire family is in on what she never doubts is a hoax, and all but positive that the money visitors deposit in the box by the door is going directly into their pockets. For Anna - a bright child, fond of riddles but otherwise living in a kind of religious dream - Lib feels nothing but distrust until the child begins to fade. When that happens, she is able to set aside her litany of Irish prejudices and face the truth: If she doesn’t do something to stop it, Anna O’Donnell is going to die in front of her.

After making my way through several recent novels written in tiresome hey-look-at-me prose (Emma Cline’s The Girls comes to mind), The Wonder arrived as a welcome relief. Donoghue’s prose is as sturdy and serviceable as a good pair of brogans, but never nondescript. There are occasional flashes of lyricism - “a cloud loosely bandaged the waning moon,” for instance, a line of perfect description couched in perfect iambic pentameter - but Donoghue’s main purpose here is story, story, story, and God bless her for it.

In the stubborn zealotry of the committee that has hired Lib and Sister Michael (the local doctor speculates that Anna is turning into a kind of plant, capable of living on air), there is a touch of The Crucible, but I was more reminded of William Peter Blatty’s The Exorcist. As in that book, each visit to the afflicted child is more terrifying. The difference, both ironic and awful, is that while Regan MacNeil is possessed by a demon, Anna O’Donnell is possessed by the suffocating dogma of the church in which she was raised. In both cases, the reader is introduced to a bright and loving child who is, essentially, being tortured to death. Anna’s plight and Lib’s efforts to save her (initially reluctant, ultimately frantic) make this book, flawed though it is in some respects, impossible to put down.

Emma Donoghue’s breakthrough­novel, the overpraised Room, was followed by a much better one, the underpraised Frog Music. (Lackluster reviews of the latter may have expressed some buyer’s remorse.) The Wonder lies somewhere between the two. We discover reasons for Anna’s fast that feel just a little too gothic and a little too convenient. I would have been happier to settle for the heavy cloak of religiosity that lay over Ireland in the 19th century (and even the 20th; see the crime novels of Benjamin Black for that). It would have been quite enough without adding the dreaded Family Secret.

Even less palatable is the distracting romance Donoghue loads onto the second half of her tale. The novel’s greatest success is realized in Lib’s twin conflicts - with the all-male committee that has hired her, and with her small charge’s stubborn determination to die, so to speak, at the foot of the Cross. This is enough for the reader, and should have been enough for Donoghue, but it isn’t. Lib (unlike Jenny Bonnet in “Frog Music”) ultimately turns to a man in her efforts to save Anna. There is a touch of the Harlequin hero in the newspaper correspondent William Byrne, who appears in Lib’s life at just the right time, and who is last seen, at least before the brief epilogue, galloping away on a horse, with his red hair no doubt blowing handsomely in the wind.

These are flaws, but not fatal ones. For the most part, The Wonder is a fine, fact-based historical novel, an old-school page turner (I use the phrase without shame). Donoghue’s grave consideration of the damage religion can do when it crosses the line into superstition lifts the narrative rather than weighing it down. In that way - as with her sturdy narrative prose, gilded about with the occasional grace-note - it also reminded me of The Razor’s Edge, only turned inside out. Maugham’s book is about the power of spirituality to heal. Donoghue has written, with crackling intensity, about its power to destroy.