It's nighttime on the Bulgarian Black Sea coast, not far from the Turkish border, and the glowing circle of wood coals on the beach is like a miniature sun. An old woman in a red-and-white gown holds aloft a battered Orthodox icon depicting a man and woman. Her face in rapture, her feet bare as she stands inches away from the burning embers, she tells the story of the nestinari.

“God, the grandfather, came to Earth. He would speak to no one, because no one was without sin. So he brought forth fire and called on all men to walk in the flames. Only one man wasn't burned: St Constantine. God and St Constantine spoke for years. But Constantine grew weary and sad. He had no wife and no family. So God brought forth the fire again and called on all unmarried women to walk in the flames. A man without sin needs a pure woman. Only St Helena endured the fire.”

Holding the icon of the two saints, the baba steps onto the coals. She walks slowly and deliberately. Her eyes are focused forward, but she isn't looking at anyone among the crowd surrounding her. She spends a few minutes on the coals: too long to attribute her tolerance of the heat simply to practice, not long enough to be totally unbelievable. She's sweating, she's murmuring to herself.

A man plays the gaida, a Balkan bagpipe made from goat skin. A drum pounds. A flute plays. Only the glowing, red-hot coals punctuate the darkness. The old woman bends down, picks up a coal and puts one on her tongue. The drum's tattoo and the wild, gyrating melodies of the flute and the gaida continue. The baba seems to be in a trance, in ecstasy. I forget myself as I watch. Later, I'm reminded the word “ecstasy” derives from the Greek ex-stasis, or to stand outside oneself. To leave one's body.

When the baba exits the fire and the music subsides, some onlookers applause. Others approach, touch her and cross themselves.

Cultures throughout the world engage in fire rituals, but the Bulgarian nestinari are unique. Only they linger on embers in order, they claim, to become possessed like oracles out of Homer's Odyssey. “In many places they play with fire, but here it is Orphean,” says Vesra Roleva, a fire walker, referring to the ancient Greek cult that believed the human race was formed from the ashes of titans vanquished by Zeus. “The nestinari are a symbol of health and luck and the longevity of the Bulgarian nation.”

Experts aren't so sure of the nestinari's origins. Some agree with Roleva that fire walkers are the modern-day remnants of ancient cults. Many link the custom to Dionysus, a God first worshipped by Thracians in present-day Bulgaria around the 6th Century BC, but whom the ancient Greeks adopted as the patron of wine and wild celebration. Other experts say Asiatic tribes brought the custom to the Balkans when they arrived in the 7th Century.

Whatever their origins, the future of the nestinari is uncertain. Bulgaria has long been isolated on Europe's political and cultural periphery. For most of its history it has faced east, towards Turkey or Russia. As more and more foreigners flood into Bulgaria's cheap beach and ski resorts, locals are devising ways to profit from the growth of tourism. Fire-walking packs in the tourists in resorts and restaurants, but raises concerns among nestinari who feel as if globalisation is cheapening the tradition.