In the fall of 1667, in the province of Härjedalen in central Sweden, a shepherd boy called Mats had an argument with the girl who was helping him to tend the flock. The girl’s name was Gertrud. It’s not known what the argument was about, but I like to think that Mats tried to kiss Gertrud and she mocked her companion, who was several years younger than her and a bit dim. I imagine that Mats’s childish pride was hurt and he pulled up Gertrud’s skirts, or maybe insulted her or beat her legs with a stick, or perhaps he even found a dry cowpat and hurled it at her. What is clear is that the disagreement got out of hand and the twelve-year-old Gertrud hit Mats. It wasn’t a very hard blow, but it was humiliating: a slap to the back of the head; a “stop-your-fooling slap” as we used to call it in my elementary school.

Mats lost his balance and ended up on his knees in the mud, glaring at Gertrud and holding back tears of rage. Thirsting for revenge, the boy ran home and told his father what had happened. In fact, he told more than that. He claimed that after slapping and humiliating him, Gertrud had crossed the river by walking on the water, with the flock close behind, and, as if by some magic art, did it without any of them wetting their feet or sinking. Somewhere between alarmed by his son’s runaway imagination and annoyed to think the girl had slapped him, Mats’s father also took to his heels and ran to the parish church, where he told the whole story to the priest.

The priest summoned Gertrud to question her. Walking on water followed by thirty-nine sheep was an accusation serious enough to merit an inflexible attitude and rigorous investigation. And, indeed, the priest must have been an inflexible man—I’m not so sure about his rigor—with a great talent for persuasion: the girl not only confessed to having walked on water, but also told an extremely convoluted story about how she’d been able to do this.

According to Gertrud, when she was just eight years old, a neighbor called Märet Jonsdotter introduced her to Satan. (That’s right, Satan: the old serpent, the angel of light.) And since then, she went on, Satan had taught her to fly, and Gertrud had, on several occasions, flown to the island of Blockula—described in contemporary accounts as an endless meadow (I imagine it as a barren wasteland) shrouded in mist—where she milked goats with the help of demons, participated in satanic rites, and kidnapped children.

The authorities then sought out the aforementioned Märet and took her into custody. Gertrud was also detained, awaiting trial.

In 1668, Märet Jonsdotter was brought before the court, accused of corrupting the young (as Socrates had been) and converting Gertrud and other girls—it seems that she wasn’t alone in her conversion and crimes—into witches. The affair quickly became a popular topic: it was spoken of on church porches, in public squares, and the muddy markets of cities. Then more witch trials were held in other parts of Sweden. The plotline was in every instance almost the same: a boy or a group of boys accused a woman or a group of women of flying to the island of Blockula, where there was a house with a table, around which they sat to practice satanic rites under the guidance of the Devil. All cases of missing children were explained: the witches had taken them to the island. As the story was repeated, further details were added. On Blockula, it was said, the witches used to dance back-to-back and did everything in reverse: they walked backwards, had sex assto-ass, the way dogs sometimes do, and they also fucked Satan, whose penis was very cold. The fruits of this copulation were frogs and snakes that the women then abandoned on the island (an infinite meadow, shrouded in mist and teeming with frogs).

For eight years, the rumor grew and fear spread. Suddenly, there were more than three hundred children who had supposedly been abducted by witches, and hundreds of women were summoned to give declarations, without the hope of anyone actually listening to what they said. The show trials were followed by executions: beheaded women whose bodies were immediately incinerated. In 1675, after a mass trial held in the parish of Torsåker, sixty-five women and six men were beheaded and burned at the stake.

Even some of the boys who made the accusations ended up receiving punishment (floggings, public shamings) for having allowed themselves to be seduced by the witches. According to Joseph Glanvill’s famous treatise of 1681, Saducismus Triumphatus, or, Full and plain evidence concerning witches and apparitions. In two parts. The first treating of their possibility. The second of their real existence, in the case of the village of Mohra, thirty-six children were condemned to be lashed on the hand once a week for a whole year. During the first weeks the lashes were administered, but as this meant the boys were unable to take part in the harvest, they began to lash them on their backs and some even had their punishment suspended.

Alarmed by the extent of the affair, the authorities convened a commission of experts to put an end to the hysteria. Sweden was at war with Denmark and the Dutch Republic (the Battle of Öland) for control of the Baltic and couldn’t afford to squander its resources on the trials of hundreds of women for having sex with Satan and his cold penis. That money, they said, would be better invested in weaponry and armies. Men should be able to fight without fear that, in their hometowns and villages, their daughters were being converted into witches.

Some of the most prominent scientists and ecclesiastics of the day gathered in Stockholm in 1676 to analyze the documents of the many courts where women had been tried for witchcraft. Carl XI of Sweden had convened the most illustrious minds in his kingdom to find a solution. The Brandenburg forces were advancing from the southwest and rapid action was needed. Those men of science were required to devise a national security strategy to stop the persecution of witches in rural and more isolated areas, where the possibility of war seemed less real than satanic influences on the island of Blockula.

Among the members of the commission was the chemist and geologist Urban Hjärne, physician to the aristocracy and author of the novel Stratonice, published just a few years before, in which he set forth the theory that true love teaches one to chastise the impure. I guess those credentials were sufficient for his inclusion.

One group of these illustrious gentlemen proposed radical solutions, such as killing all single women over the age of thirteen in order to root out the cancer of witchcraft before, as a nation, setting out to trounce the Brandenburgers.

Another member of that council, possibly the most liberal of all, was the theologian Eric Noraeus. He led the faction of wise men who advocated for declaring all the witches innocent and so putting an end to the farce with a stroke of a pen. This was not because the cleric didn’t believe in the seductive powers of the Father of Lies, but rather because the descriptions of the island of Blockula given by the accusers seemed to him highly improbable (an infinite meadow, shrouded in mist, and teeming with frogs?).

In that group of illustrious, skeptical thinkers there was also a botanist from the province of Örebro. His name was Olof Bromelius.

After deliberating for a few weeks in the sumptuous chamber of a small palace in Stockholm, the commission reached a series of preliminary conclusions. To start with, it ordered the style of the interrogations to be modified: rather than requesting the children to confirm their initial statements time after time, they were asked to repeat them. The children contradicted themselves and, eventually, retracted their accusations. From this came the modern science of interrogation, as criminologists term it, and the great Swedish witch hunt ran out of steam.

When the task of the commission of wise men was completed, the government asked priests throughout the whole country to inform their parishioners that all the witches in Sweden had been eliminated or exiled from the territory for life. Barring a few isolated cases, the persecution gradually abated over the following years and Sweden entered the modern age with a firm step, or at least that was how it seemed.

Happy to have offered his services to his country at that important moment, Olof Bromelius returned to his work as a botanist and numismatist. He made a thorough, systematic study of the flora of Gothenburg, amassed an important collection of coins, and died on February 5, 1705. The Bromeliaceae family, that is to say, bromeliads, is named in his honor.