Somewhere past Tehran, beyond the void known as the Great Salt Desert, Brian Murphy arrived at a field of wild madder.

He had been tracking the history of Persian carpets since 1999, between assignments in Iran and Afghanistan for the Associated Press. His vivid memoir, "The Root of Wild Madder" (Simon & Schuster), tells of visits to bazaars, readings of the mystical poet Hafez and arduous treks, all of which failed to explain the swirling patterns and complex colors that village women weave and elite museums collect.

He hoped the madder plant, a dye source known to botanists as Rubia tinctorum, would unlock the ancient mysteries of rugs, and by extension, illuminate cultures known the world over for their brilliant craft.

"Carpets offer a continuity between now and the past," Murphy said recently by phone from his home in Greece.

His book is a travelogue in the best 19th-century tradition. With madder as grail, Murphy set out to get to the bottom of a Turkmen folk saying: "Carpets are our soul." He made 25 trips in five years, to Mashad, Herat, Badghis province, Mazar-e Sharif and other locales in Afghanistan and Iran, where rugs are still hand-made. Readers are treated to a precarious ride through the mountains in blinding sleet. Murphy sips tea with a warlord and trades cigars for a meal of pilau. He also flies to New York, so a Fifth Avenue dealer can unroll a stunning Heriz silk carpet, for which a Wall Street trader is said to have paid $80,000 in 2004.

Madder was seductive. It grows from roots the color of blood, which were pounded for centuries into a dye potent enough to color wool and bones. Synthetic dyes long ago proved more efficient, so Murphy was delighted to find a field of madder in a remote region, and a massive stone grinding wheel that crushed the roots into paprika-colored dust. Madder dye can produce a range of hues from orange to purple, all of which mellow over the years into a pointillist palette that modern collectors covet. Synthetics always seemed garish by comparison.

The struggling dyemaker had modernized his equipment, trading camel power for a tire linked to a motor. The author acquired a few brownish-red roots as souvenirs, and blood-red creases in the palm of his hand, but no epiphany.

Only much later would Murphy encounter a young singer and weaver named Zeynep, from the nomadic Qashqa'i tribe. She came as close as anyone to explaining the riffs of knots. In her hands, shapes and colors were not random twists of wool, but memories being recorded -- a bird she saw as a child or the color of a mountain she knew.

"It's an inner song," she told Murphy.

There is mystical clarity in her explanation that the rug he sees will never be the one she made.

"The Root of Wild Madder" gives minor roles to Genghis Khan, the disastrous British retreat over the Khyber Pass, the Iranian revolution, the Taliban and Pentagon-sponsored flyovers. But carpets -- rolled, stacked, dusty, sand-caked, sun-bleached or silken -- are the stars in this drama.

Journalistically, investigating carpets proved helpful. Tracing the origins of a dwindling craft opened avenues into the economics, culture and social dynamics of the region. The journey also introduced Murphy to a world of people "beyond the talking heads and dissidents we all have to cover," he admits.

Three stories stand out. In Afghanistan's Turkmen belt, he met a family of Saryk rugmakers. In 2003, a 19th-century Saryk carpet sold at Sotheby's for $24,000, a staggering sum in the bleak province of Badghis, where two sisters and a cousin worked at a loom that covered an entire room. They were making a dowry for the eldest girl, whose weaving skills enhanced her prospects for marriage. Rugs are now made for income. But Murphy, who had been seeking understanding of their mystical and spiritual dimension, asked whether the girls believed carpets had a sacred aspect.

"There are times when I finish a difficult border or gul and must stop just to look at it," Asli, the eldest, replied from the floor. "It is like a small world all alone and separate: perfect and peaceful. God must be guiding our hands, I think. This is how he gets us to look beyond this world."

During a sandstorm, a man named Rahmin sheltered Murphy under a carpet his grandmother had made. Rahmin told of whispering into the carpet after her death, believing his grandmother could hear. To him, carpets contained lives. And yet, when the opportunity arose, minutes later, to barter the rug for food, he tried.

"You cannot eat memories or stories," he told Murphy, "no matter how sweet."

On a trip to Iran, Murphy received the gift of a small, unremarkable carpet from a grieving mother. Her son had been killed in a minefield while trying to reach the European Union. He got as far as the border between Turkey and Greece. She was weaving the rug when he left and thinking of him constantly, she said. Murphy took it home with him to complete the son's journey.

"Maybe something of my son is still alive in his carpet," she said. "If it makes the journey, maybe he will rest peacefully."

Murphy is now the AP's international religion writer. His collection of 40 carpets, kilim and other textiles reminds him daily of the anonymous artistry of hopeful girls and worried mothers in heart-rending villages.

"They have this amazing compendium of life, spirituality," Murphy says. "I hope people will see them as more than an object. I hope they will see them as an extension of a culture, and try to recognize the humanity that goes into making them."

Brian Murphy, author of "The Root of Wild Madder," traveled Iran and Afghanistan, tracing the origins of carpet weaving by nomads such as those at left and the mystical and spiritual dimensions of the rugs. Inset: the madder plant, source of red dye.