The Good Mother by Rae Cairns is a thrilling read by a debut author

The Sydney-based mother of two remembers a soccer game where her then five-year-old son Ben was physically threatened by a parent from the opposing team.

"I charged onto the field, leapt in front of my son, fists balled, and told the man in no uncertain terms to step away," she says.

The slightly built Cairns says she just felt a rush of heat and acted on reflex.

"There was no 'what should I do' moment, just instinct."

Years later when she decided to write a novel, she remembers the sentence "Show me a soldier who will fight harder than a mother to save her son" flew from the tips of her fingers onto the page as she wrote the final scenes.

"I realised that one sentence had succinctly captured a major theme of my novel."

Sarah Calhoun is no ordinary mother. Well she is and that's half the fun. A divorced "soccer mum" of three living in the eastern suburbs of Sydney, an ex-husband who's a decent bloke. At 39, she's the strongest and fittest she's been in years, a runner with thick curly hair and a labrador puppy. It would be easy to hate her.

But she has quite a few secrets no one knows about and when her past catches up with her, she can't outrun it.

Calhoun used to work in Northern Ireland, as a youth worker with troubled children, and when two men from from her past knock on her door, she's forced to head back to testify in a murder trail.

Will she lie and allow a killer to walk free or will she tell the truth and place her family in the line of fire?

And here's where the story gets really interesting. Much of this story is based on Cairns' real-life experience.

In her mid-20s, in the late 1990s, she volunteered to head to Northern Ireland to work as a youth worker, mentoring disadvantaged youth, many of them children of the paramilitaries in the final years of The Troubles.

She was working in Crossmaglen, a republican stronghold known as "Bandit Country", controlled by the Irish Republican Army.

"The village could be very intimidating," she says.

"I'd take the kids for a walk through the countryside and they'd train the guns on us for fun.

"There were tanks and soldiers and just with general tension and unease."

She began dating a man she thought was the one, only to accidentally find out he was a dedicated paramilitary member and she broke things off.

"The questions lingered for years, what if I hadn't found out about his allegiance, what if the relationship had never been real, what would happen if our paths crossed today."

Cairns used these questions as the springboard for The Good Mother. She wrote the first draft, completed a year-long writing mentorship program, signed with an agent and sent the manuscript to a publisher.

She was then struck down by rheumatoid arthritis and reacted badly to the prescribed medication.

"I couldn't even speak a coherent sentence, let alone write one."

It took two years before she was feeling better but the manuscript had moved no further.

In December 2020 she self-published The Good Mother and in July 2021 it was shortlisted for best debut crime fiction in the Ned Kelly Awards, the annual awards which recognise the best crime and true-crime writing in Australia.

Two weeks later she signed with another literary agent and was offered a two-book deal with HarperCollins.

This edition of The Good Mother has been finessed again, there's an extra 10,000 words and new scenes.

"It's been a long process but I wouldn't change a thing," she says.

She says using her past experience as the inspiration was challenging at times.

"When I got home from Northern Ireland, I just bundled it all under my bed, like everything, my photos, my diaries, my letters home, every single memory. I forgot about it and got on with life.

"And then when I sat down to write, initially I was like I'm just going to be very clinical.

"But when I went through everything, all these emotions came flooding back.

"I was writing the scene about the riot, that was the hardest thing to write, because I knew to make it work I had to draw on the sensory memories of the riot that I got caught up in. That raised stuff for me.

"There are elements, it feels very extreme to say it, but I guess PTSD, in a sense, I still hate helicopters flying overhead, some things take me back there instantly.

"But writing the book has also given me the opportunity to put it behind me again, I guess.

"Sarah is not me, but some of her experiences and the way she works through some of her own issues are very similar."

She's happy to admit she doesn't completely understand the situation in Northern Ireland, few people do.

"I kind of think everyone went, they've agreed on peace, and the majority of people wanted to get on and lead normal lives, but people on the extreme fringes were left behind feeling really dissatisfied, on both sides.

"When there's so much generational trauma, it's really hard to heal and when there's any change to the status quo, for example, Brexit, or changes to trade agreements, it's been 20 years since the Good Friday Agreement, and just this week Sinn Fein, the Irish Republican political party, won the election, it opens old wounds and fears on both sides."

Leaving the politics behind, she's also fascinated by the idea of what makes a good mother.

Sarah makes decisions in the book, even before she gets back to Northern Ireland, which are easy to disagree with, or hard to understand.

"Society puts a lot of judgements on mothers, other mothers put a lot of judgements on other mothers," she says.

"There's a lot more going on than what we see on the surface, what people present to the outside world."

Cairns wanted to put her heroine in situations where the reader might go, "that's taking it too far", asking herself how would an ordinary person deal with that situation.

"She's got no special skills, she's not Liam Neeson in Taken or anything, she's not Jack Reacher.

"I like that question of how ordinary people, ordinary women in particular, would deal with extraordinary things."