In a world that is easily recognisable as ours, a major scientific breakthrough has ensured that boys born with a particular gene can be identified as having the potential to grow into violent men. This gene, known as M+, can be identified in baby boys with the use of a simple DNA swab of the mouth.

While this discovery has implications that could bring about widespread changes in society - particularly with regard to domestic violence - it quickly leads to a split among those who support the test versus those who find the Idea invasive or problematic. Nevertheless, within the space of few years the test begins to determine the fate of young boys - their access to schools, careers, relationships and, perhaps most importantly, how they are being judged by the adults around them.

In this situation, we are introduced to two sisters, both of whom give birth to boy children, quite close in age. Antonia is the wife of a doctor, Owen, who coddles her son, Jack, to a degree that her sister Bea considers ridiculous. Antonia also choses to have her son tested (Jack turns to be M-, and does not carry the dangerous gene). Antonia and her husband then go on to open a clinic for M+ boys, and become very wealthy in the process.

By contrast, Bea and her partner Alfie decide, on principle, not to have their son Simon tested. But this leads to years of a situation where Simon is effectively treated as M+ by default, as he does not have a test result that can prove otherwise. Bea's social circumstances are the opposite of Antonia's, and the two boys each have access to a very different set of resources as a result of this.

Nevertheless, the cousins remain close. But as Simon and Jack approach adulthood, years of closely-held family secrets and the very different choices made by their mothers begin to play out in a dangerous fashion.

At its heart, this book is about the sacrifices that mothers make for their children - and what being a good mother really means.

The narrative is frighteningly plausible, and raises major ethical and social issues, beyond the already-complex minefield of parenting successes and shortcomings. Jayne Cowie has delivered a gripping read which engages the reader's interest until the last page - particularly since the story goes turbo, hitting its stride (and how!), in the last few chapters. If you want a breathtakingly engaging read with just one major speculative element, this is definitely a book worth reading.

This book is so thought provoking and a real conversation starter. It is a dark, dystopian thriller which asks how far a mother will go to protect their child.

The story is set in a society where scientists have discovered a genetic predisposition to violence based on an M+ result. Young boys are tested and their status in society revolves around this result. The book focuses on two sisters who each parent a son; one is an overbearing, married, successful, mother of a mollycoddled M- boy. The other sister is a financially struggling, single parent to a non tested son. It brings the nature vs nurture theory into mind The book timeline moves back and forth throughout so the reader can see how life events, government decisions, society and the relationship between the sisters change.

As a parent I found this book extremely thought provoking and at times heartbreaking. Untested boys are treated as guilty unless proven innocent (with a negative test) and are discriminated against alongside the M+ boys. The segregation was really difficult to swallow.

The book is not like anything I have read before and I have a feeling it’ll stick in my mind for quite some time. I would have liked another chapter/ epilogue about Simon but i understand why the author chose to end the book the way they did.

Thank you to Netgalley @netgalley for this e-ARC. Publishing date 31/08/2023.