The enlightenment has been a pervasive theme of this year’s Edinburgh International Festival. In The Last Witch (a co-production with the Traverse Theatre), we are presented with its negative image: a descent into a pre-rational world, and a pretty benighted one at that.

Rona Munro’s new play gives an account of the life and death of Janet Horne, who was burnt for sorcery in Dornoch, Sutherland, in 1727, just nine years before the Witchcraft Act made such executions illegal. Her feet immersed in a barrel of tar, the poor woman perished in a manner that was brutal even by the standards of the time. The sketchiest of historical records exists about the Horne case, making her an ideal screen on which to project modern concerns. In Munro’s imagining, she becomes a spirited and sharp-tongued widow, bringing up her crippled daughter alone and cursing her neighbours when they complain about her stealing their peat. Kathryn Howden’s Janet bursts with buxom vitality, switching unsettlingly between laughter and spite.

Is Janet’s supernatural gift genuine? Certainly she believes she can turn herself into a bee, while her daughter, Helen (the excellent Hannah Donaldson), is convinced she has been made into a flying pony. On balance, though, we are given to believe that her powers rely on a mix of showmanship and folk medicine, and that her real crime is to be poor and female, yet not subservient.

All fair points. The trouble is that this sociological explanation for witchcraft has become so established, it all seems a little obvious. No surprises that Janet’s prime tormentor should be an army officer with his own psychological demons; nor that the local minister should acquiesce in this persecution. More interesting, if never quite developed as it might be, is Helen’s story, which sees her make a Faustian pact with a man who may, or may not, be the Devil himself.

In the end, like the lightning that erupts over the stage whenever Satan is invoked, The Last Witch is a flickering affair. Studded with some memorable writing and given a production by Dominic Hill that is at times genuinely creepy, it fails to cast a spell.

Royal Lyceum, Edinburgh