Sometime during the 12th century, two children appeared in the village of Woolpit in Suffolk, England, seemingly out of nowhere. These were no ordinary orphans: The boy and girl spoke in an unknown tongue, sported strange clothing, and only ate raw beans. Oh, and their skin was green.

The green children’s story began when they emerged from one of the wolf-trapping pits for which the town is named. The pits—designed to lure and ensnare dangerous wolves—were likely at least twice as tall as the children and a couple hundred square feet in area. A reaper discovered the pair and took them into town, where Sir Richard de Calne gave them a home. In time, they lost their viridescent pallor and diversified their diets, though the boy became increasingly depressed and sickly before succumbing to illness and dying.

When the girl learned to speak English, she relayed the story of their underground homeland—St. Martin’s Land—where everything was green and it was always twilight. According to the girl, the boy was her brother. In one version of the story, she said that the siblings had been herding their father’s cattle when they heard a loud noise and suddenly found themselves at the bottom of a wolf pit. An alternate report states that the children had followed the herd into a cave and had become disoriented. The sound of bells led them out, but when they emerged from the cavern, they did so in Woolpit rather than St. Martin’s Land.

Historians have stitched the Woolpit narrative together from the reports of Ralph of Coggeshall and William of Newburgh. Although neither man had firsthand experience with the Green Children, and their secondhand retellings differ in their details, the overall story is the same. Ralph was a sixth abbot of Coggeshall who lived in a nearby county and had repeatedly heard the story from Richard de Caine himself. He wrote of it in the Chronicon Anglicanum around 1189. Monk and historian William of Newburgh’s Historia rerum Anglicarum also contains the story of the children, though he was more removed from the incident both physically and in time: His version was published circa 1220 and reportedly came from many “trustworthy sources.”

Even if you prefer one account over the other, a larger question remains: is this story a folktale or some botched version of actual history?

If the story is based on actual events, there are a few plausible explanations for the green tint. One theory is that the children had arsenic poisoning. The story goes that their caretaker, an earl from Norfolk, left them to die in a forest near the Norfolk-Suffolk border. Another more likely (and less depressing) culprit is chlorosis, a type of iron-deficiency spawned from malnutrition that leads to a greenish complexion.

Yet another (and perhaps most likely) theory postulates that they were the children of Flemish immigrants who were persecuted and killed—possibly in the battle at Fornham in 1173. Fornham St. Martin was a nearby village, separated from Woolpit by a river and just a few miles from Bury St. Edmunds, where loud bells often chimed. It’s possible that the children had been orphaned, suffered a poor diet while lost and on their own, and eventually made their way to Woolpit from Fornham St. Martin by following the clanging bells.

Whatever the children’s origin, the sister eventually became integrated into English society. She was baptized and allegedly later married a man at King’s Lynn, possibly an ambassador of Henry II, though conflicting reports say she became "rather loose and wanton in her conduct." She may have taken the name “Agnes Barre,” though as with most things in the story of the Green Children, there’s simply no definitive evidence.