When author Niamh Boyce was 19, she landed a job archiving the Leinster Leader. One day, she spotted a story "no longer than the width of a thumb" about a court case. Dating from May 1942, the report concerned a "coloured man arrested for serious offences against girls".

Boyce made no note of it, but despite its brevity, the image of the man – and what he had done – stayed with her. When she began to write almost 20 years later, he doggedly returned to her mind, until she couldn’t ignore him.

Boyce's debut novel The Herbalist concerns an exotic potion and tincture seller, who arrives in a midlands town and sets up a market stall. Before long the townsfolk, particularly the women, are beguiled by him. A strong cast – a prostitute, an ageing wife desperate for a child, two young girls who suffer similar fates – dominate a story that is sharply rendered, and full of dark humour.

Boyce perfectly captures the hysteria in the town's see-sawing obsession with the herbalist. "The market in the real case was in my home town so I could really visualise him," she says. "I also thought about [Arthur Miller's play] The Crucible . . . about mob mentality and how a town can scapegoat someone".

Boyce stresses that the novel is completely fictionalised, because she was fearful of “trespassing on people’s real lives”. Her story is set slightly earlier, in 1939, and subtly examines the class structures of Irish life, and the sense of predestination that comes with being born into a specific background.

“That structure was still there when I went to school in the 1980s,” says Boyce. “We were all still divided into groups according to whether our parents were farmers or shopkeepers.”

“Emily [a young girl who becomes obsessed with the book’s title character] has no standing and is a nobody. When you live in a small town, before you’re born you’re ‘one of the Kellys’. The day you start school is a new experience, in a new place – but not to the nuns who teach there and know exactly who you are. The herbalist character represents what an outsider can do – he sees Emily in a different way.”

A late starter
Boyce considers herself a late starter as a writer. Born in Athy, she lived in Galway for 14 years, before moving closer to home, in Ballylinan. After jobs as a community development officer and library archivist, she gave up work to have a family (she now works part-time).

In 2009, she started writing, and was 37 when her first short story was published. Boyce is almost surprised that she is a writer, as her first love is art.

“I kept diaries, painted a lot and was sure I’d be a painter. The artist Louise Bourgeois gave me hope because she didn’t start working seriously until her 30s. I also did a workshop with writer John MacKenna – having never written a short story – and with his encouragement, I began to write.”

Before the publication of this novel, Boyce won the Hennessy Prize for fiction last year, with her story Steps of Stairs. It was, she admits, a short work, "written at a kitchen table with a child climbing all over me". Anne Enright has spoken of similar juggling of young children and writing, and Boyce feels an affinity. "It's not the worst way to write. I would not have written as intensely or sharply, with that pressure, and I wanted to finish it. The brevity suited it."

The first draft of The Herbalist was written quickly, over a summer. An energy – from where, she's unsure – propelled her on, and the narrative addresses social issues that still resonate today: more than one character has an encounter with a Magdalene Laundry.

“I was very young, but I remember the Anne Lovett story, and growing up Nell McCafferty was the only woman I ever saw on TV, speaking seriously. It was a very male world and women nowadays forget what it was like for previous generations. We’re lucky to be liberated and forget what it was like for our mother’s generation.”

Through a local historian, Boyce discovered that the real herbalist – a man called Don Rodrigo DeVere – was charged with “procuring miscarriages” for women. The current debates about women’s reproductive health and abortion are divisive, and make her angry. “The whole debate is not simple and our language – pro and anti – can’t even accommodate the issue. It’s too adversarial,” says Boyce.

The idea of motherhood becomes a complex issue for several of the book’s characters. Boyce has three children and bristled when she discovered that a local newspaper defined her as that.

"I didn't want them to focus on my family situation. They said I was a 'mother of three' – I am, but I'm also a writer". And one who writes of complicated issues with verve and passion.

The Herbalist by Niamh Boyce is published by Penguin