When Polygon approached acclaimed writer Jenni Fagan to be part of the Darkland series (a collection of books based on real or fictional accounts of Scottish history), she immediately knew the North Berwick witch trials would be her inspiration. The result is Hex, a powerful short novel that deftly conjures up a séance between two witches, Geillis Duncan on the night before her execution in 1591 and Iris, a contemporary witch. As Duncan's clock ticks onwards, the two women enter into a tug-of-war of comfort and control, compassion and clear-eyed anger.

To tell the story of a person who once lived and breathed is a great responsibility. Some writers wear that responsibility too lightly, but Fagan isn't one of them. In taking Duncan, a maidservant accused of witchcraft by her employer, as her protagonist, she has created a nuanced and sweeping picture of a young girl tortured, abused and sentenced for the most spurious of reasons. Iris says, 'I'm not a tourist, Geillis. I'm not a visitor in a real person's life.' So too can you feel Fagan resisting the lure of spectacle or exploitation.

The complexity of Duncan's character is conveyed economically and Fagan resists a simplistic view, even though the historical records we have paint a straightforward picture. She worked for bailiff David Seton, who interrogated and tortured the young woman until a 'confession' was forced from her. At the time, King James VI (who had recently published Daemonologie, a compendium on witchcraft lore) was undertaking a treacherous sea journey on his return from Denmark.

Sorcery was blamed for the storms and Seton found himself with the perfect excuse to please his king. He offered the mistreated and tortured Duncan up as a source of entertainment, forcing her to play a jaw harp (then known as a Jew's Harp) in the monarch's presence. As the first person on record to play that instrument, the details of Duncan's fate are accessible to us now. The same can't be said for the majority of women who were tried and convicted of witchcraft.

This is a wrong that Witches Of Scotland, a campaign to pardon these innocent people, is trying to address. In Hex, Iris says, 'I like to think about what would happen if the women of now went out to march for the women of then.' The women (and men) of now are doing just that. The pair behind Witches Of Scotland, lawyer Claire Mitchell and writer-teacher Zoe Venditozzi, are raising the profile of this campaign through a series of governmental petitions as well as podcasts, which serve as a fascinating educational resource.

The idea was born when Mitchell was reading about witch hunts. Venditozzi explains that 'she read one particular confession where the women said "is it possible for you to be a witch but not realise that you're a witch?" and, knowing that torture was employed in Scotland at the time, understood it to strongly suggest that people were being tortured until they would say just about anything.'

The Witches Of Scotland campaign is focused on the fact that normal women and men (although overwhelmingly women) were accused of witchcraft with a complete absence of evidence while torture was heavily relied on to obtain confessions. What could an accused person say to save themselves? Nothing, but they can be forgiven for trying. This absurdity features heavily in Hex: 'bring upon a woman only shame. Make sure there is nothing she can say that could be taken as truth.'

In her novel, Fagan particularly excels in the translation of fact to fiction. 'I write stories without limits,' says the author whose well-received 2012 debut The Panopticon was later turned into a play which Fagan herself adapted for the stage. 'I'm really harsh about making sure I have a strong foundation in the subjects I'm approaching. Then I'm free to write in a space that's kind of beyond knowledge. Afterwards, I go back with a clear and critical eye.'

She also thinks there's a lot to learn from these women's stories and from the policymakers who exploited the law for their own gain then and whose influence continues to be reflected today. In contemporary Scotland, equality between the sexes is supposed to be a given. We feel that, as a society, we have evolved. But that assumption doesn't leave us much space to question our experiences and, as Fagan points out, it can be something of an illusion that doesn't serve men or women particularly well.

Reflecting and reassessing the stories of our past can be a conduit to future change, and it's through the efforts of today's ordinary people that those from the past can be recognised as real humans with complex inner lives. As Iris says in Hex, 'silence is complicity. Non-action is a form of approval.' And later, 'they would kill her rather than hear the truth that the people in charge are liars.'

Witches Of Scotland hopes to achieve an official pardon and apology for all of those accused and convicted of witchcraft. The organisers would also like to see the construction of a national memorial to respect their memory. This campaign has gathered the support of many, including author Sara Sheridan whose 2019 book Where Are The Women? helped inspire Mitchell's desire to draw attention to this significant moment in our history.

Fagan has contributed to this cultural discourse with a short novel wielding a heavy emotional punch. As all the best books do, it leaves the reader drawing parallels between the world depicted and the one they live in, and how they can continue to survive and thrive. The answer can be more modest than expected. As Fagan says, 'you don't have to be able to do something big to change things. I do firmly believe that every tiny action can make a huge difference.'

Hex offers a perfect reminder that words have power. An accusation, a pardon, a work of fiction: all have the potential to change the course of a life or a moment in history.

Jenni Fagan: Hex is published by Polygon on Friday 4 March; news on the Witches Of Scotland campaign can be found at witchesofscotland.com