On April 10, 1834, so the story goes, a fire broke out in a mansion in the old French Quarter of New Orleans. According to one version of the tale, when the neighborhood poured out to rubberneck and offer help, they noticed something odd (by 19th century southern elite standards): the woman of the house was trying to save her jewels and furs without the aid of her slaves. When asked where her servants were, she told everyone to mind their own business. Some said this was mysterious enough. Others said they heard faint moans and screams from the attic. Either way, a small brigade took it upon itself to bust into the house and find the woman's slaves. Yet when they opened the door to the attic, they stopped dead in their tracks—some vomiting from the stench.

Heaps of corpses, organs, and limbs. Slaves pinned to tables or cramped in small cages. Live bodies with their eyes gouged, fingernails torn out, ears hanging by shreds of skin, or their mouths filled with animal shit and sewn shut. People flayed of skin with festering wounds. Many accounts claim they found one woman whose skin had been peeled off in spirals to make her look like a caterpillar, another with her bones broken and reset so that she looked like a crab, and one more whose intestines had been torn out and knotted around the waist. Many of these victims (some claim there were up to 100) were supposedly still alive—putrid and starving.

Yet many believe rumors of the deaths LaLaurie wrought have been greatly exaggerated. Some historians, eager to contradict portrayals of LaLaurie as inhuman, have tried to fully exonerate her. But the truth lies somewhere in between the fiendish legend and the saintly expungings. LaLaurie was certainly a monster, but she was (probably) not insane, or even incredibly unusual for her time. Like some Lovecraftian god, she was and is terrifying because she was a living fossil—an unabashed emanation of a particularly barbaric form of slavery that was briefly common in parts of Louisiana.

Some try to explain LaLaurie's descent into depravity by way of her third husband, Louis LaLaurie (who was not related to her before their marriage), a younger doctor freshly arrived from France. He knocked up the richer LaLaurie, then married her after their child was born in 1826. Soon after their marriage began, stories of her abuse against her slaves started to emerge. Residents filed complaints leading to investigations for cruelty to slaves (New Orleans had unique laws theoretically protecting chattel servants more than in other parts of the Deep South) in 1828, 1829, and 1832. Some say she began beating her daughters when they tried to feed them, although she put on a kind public face.

Those inclined to absolve LaLaurie take this line of logic (that the Mistress was driven to insanity and violence by Louis) to its extreme. They argue that Louis (who some suspect was experimenting with Haitian voodoo potions to create more docile servants) turned away help from the fire, as he was the one mutilating the LaLaurie slaves in cruel half-medical experiments.

"The plantation owners [of which LaLaurie was one] were living in terror," explains Daniel Rasmussen, the author of American Uprising, a history of the 1811 slave rebellion. "They were terrified by Haiti. They had read the newspaper reports—once a week or so there's some story about rapes, beheadings, brutality against whites in Haiti. And they think if they don't crack down and keep their slaves under control, what happened in Haiti will happen in New Orleans."

"The forms of punishment were quite extreme. The 1811 revolt saw over 100 slaves beheaded. Their heads were put on poles stretching for 40 miles from the center of New Orleans out into the countryside. You'd see slaves' corpses from the rebellion dangling from the city gates."

This growing sense of panic and unease probably explains why none of the investigators called in to check on LaLaurie's cruelty or ever charged her with anything— until 1833, that is. That year the mistress apparently grew enraged with a 12-year-old slave girl, Lia, who tugged at a snag while brushing the Mistress's hair. She chased the young girl around with a whip, and the tween chose to jump off the roof rather than face a thrashing. Witnesses saw LaLaurie burying the girl's mangled corpse, so they were forced to fine her $300 and make her sell her nine slaves. But they looked the other way ( as they did in most slave cruelty cases) when LaLaurie had her family members buy back her slaves, transfer them to her, and compensated them for their expenses. For all the anti-cruelty laws, a good degree of violence was tolerated. So nobody would have recorded exactly what was going on in the LaLaurie household in the years before the fire, because it all probably just seemed like your standard post-1811 slave punishments.

Then the LaLaurie Mansion fire broke out in 1834. That episode is actually well documented in the newspapers of the day. Folks did get irate at LaLaurie for not opening her attic to free her slaves, and what they found did shock them. But the original accounts are a far cry from crab women and intestine belts, although they're still far from pretty and exonerating stories:

Slaves were found, chained, scarred, and starving. One paper noted that seven were suspended by their necks and badly mutilated, while another mentioned a man with a hole in his head filled with maggots. They had bloody welts, were living on gruel, and wore iron collars with inward-facing spikes, which seems like a tableau pulled from an archetypal medieval torture chamber.

Yet according to Rasmussen, these were fairly typical forms of restraint on the plantations outside of New Orleans, where rural landholders feared that their slaves would grab their field machetes at night and come for them in their sleep. So they exercised extreme brutality regularly.

"They would tie your hands to four stakes, then whip you with a cat-o'-nine-tails. And that would leave you bleeding and barely able to move," says Rasmussen. "They also had iron masks to put around your head so you couldn't eat. And they had collars with spikes facing inwards so the slaves couldn't sleep without getting spikes stuck in their necks. Those were common forms of punishment in Louisiana during this period. They believed that without the threat of tremendous violence, slaves wouldn't stay slaves."

Normal or not, a mob of nearly 4,000 people still felt that this violence was egregious enough to ransack LaLaurie's house on the spot, looting and pillaging in disgusted rage as the fire burned. Rasmussen suspects that by this time, over 20 years removed from the violence LaLaurie had grown up with and secure inside the safety of a now established and well controlled New Orleans, people had started to lose their fear of slaves, distancing themselves from the harsh punishments of the countryside and coming closer to the genteel image of protective and soft slavery promoted in things like the local legal code under which LaLaurie had been investigated.

Whatever the source of their shock, they seemed hell bent on punishing LaLaurie for her overzealous application of an already extreme form of punishment. Yet in the fracas, she escaped with her slave driver Bastien to the docks where she fled to Paris. Some believe that she died there in 1842 or 1849, and was disinterred and moved to a cemetery in New Orleans in 1851. Others believe she faked her death in Paris so that she could secretly return to Louisiana and keep on carrying out her cruel life secretly. Others believe she never really left. It's all a mystery.

But many people didn't really care what happened to LaLaurie. She was more useful as a legend than a clearly identified corpse. Her story was picked up in papers in the north, catching the eyes of outsiders like English writer Harriet Martineau who traveled to New Orleans in 1836 to collect stories about the Mistress in an attempt to explain her cruelty. It was this quest that yielded many of the post-facto accounts of her foul temper, including the tale of the death of the 12-year-old slave girl. And from there people further elaborated and embellished their hindsight tales, creating a body of local lore anthologized in horror stories by the end of the century and strung out in even gorier half-truths by tour operators in the past century.

Yet we do know a little bit about LaLaurie's later life thanks to the correspondences kept by her children. The story they tell is of a woman resettled in Paris and living a quiet, harmless life. She apparently never expressed more rage or violence (at least there's no record of it) nor understood why she had been driven out of New Orleans or realized the implications of her violence.