It was a warm evening and I was in another world. Dark had fallen and there was no moon. I sat perched on a rock, Indian style. Above me, on both sides, black jagged mountain peaks pierced the star-studded enormous black sky. Below, further down the valley, and above, there were dots of lights ¿ fires from the Tarahumara Indian caves and log cabins. Occasionally, a dog barked or a voice carried through the canyon from far away.

Looking up at the stars I remembered a legend a Tarahumara had told me: "The stars are Indian girls, very beautiful, who were shot by arrows into the sky. The girls cling to the arrows and adorn the heavens." As I quietly sat there on my rock I realised that I loved this strange Indian world, having returned for the fourth time during a 15-year period.

About 50,000 Tarahumaras live in caves and log cabins scattered to the winds throughout the twisting gorges, canyons, plains and valleys of this southwestern third of the State of Chihuahua. They have preserved a staccato-sounding Uto-Aztecan language and, yes, their ancient spirits hover and a Tarahumara shaman has powers, as I observed.

On foot I was travelling with a young Tarahumara woman, Felicitas Guanapani, to Ojachichi, an Indian settlement in the highlands where, 11 years earlier, I had met her father Juan Guanapani and his family. Back then I arrived on horseback with a Jesuit priest, Padre Luis Verplancken. When we left we brought with us Felicitas who was then six, to take her to a mission school. I was to be her sponsor.

Felicitas now lived in the town of Creel where the Sierra Tarahumara begins, and we walked to Ojachichi together. Felicitas, now a fully grown woman, had learned perfect Spanish as well as English.

It was late the next day when we arrived at an old adobe mission church which sees a priest once a year at most. I was to stay at a drafty, ancient log shack reserved for the priest. Felicitas left me here, alone, and walked downstream along the river to her family's log cabin nearly a kilometre away.

That night the moon was full at Ojachichi (which means 'Place of the Bears'). The time-carved rock-face over the caves across the river reminded me of ancient Egyptian temples. Frogs, oblivious to the bitter cold, were giving a croaking concert. I saw a coyote cross a clearing less than a hundred yards away. He barely turned his head to look at me and continued on his way.

A cave across the river was lit up by a log fire. The sounds of a drum, voices and a simple flute seeped out of the cave. Monotonous and repetitious, the drum and the flute managed to create an eerie, haunting feeling . . . I remembered that Felicitas' father had told me about the spirits who lived here; about the fireball that occasionally zoomed around the church, about the human spirits who lived in animals like the coyote and the crow. I would have felt better not being alone here.

The same flute and the drum woke me up very early in the morning. As the sun came up they abruptly stopped. A little later I got up, went out and looked across. There was no trace of anybody, no fire, no smoke. Rubbing my eyes did not help!

As the sun rose, taking the bitter chill out of the air, I walked downstream to the home of Juan Guanapani. He was sitting in front of his little log cabin ponderously reading a Bible. Juan asked me whether I had slept well. I told him about the coyote I had seen passing at night, and about the light from the cave with the drum and the flute and how everything had vanished, evaporated. Juan looked at me with a curious half-smile, then said: "The family who lives there left a month ago." He shrugged and offered no further explanation.

After a Tarahumara breakfast consisting of a big drink of 'pinole' (made from popped corn which is finely ground and then mixed with water) served by Felicitas in a gourd, Juan and I decided to go and look at some cave paintings he had promised to show me.

Strange, enormous insect-like creatures and life-size figures that resembled humans were done in red ochre on a big surface of rockface just above a river bed. Neither Juan nor anyone else could tell me anything about them, except that they were 'from before'.

A friend of Juan's who lived in a small log house near by had joined us. "There are some more further up," he told us. We went off to have a look, leaving behind one of my cameras mounted on a solid tripod.

On a rock next to what looked like an old grave there was a stiffly drawn hand in fading red ochre. Juan's friend threw a pebble towards it from a good distance and said: "There it is." Juan and I walked towards the rock but the man exclaimed: "Don't go near it! Something might come out of there." Juan stopped dead in his tracks. I walked up a little closer and had a look. It was not really worth photographing, I thought. Juan said: "He tells me that many times at night they see strange creatures come out of there." I laughed it off and Juan chuckled ¿ but only politely.

We returned to where I had left my camera. Incredibly, camera and heavy tripod had tumbled over and lay on the ground. No damage was done, but this had never happened to me before except in a storm. There was no wind . . .

Two days later I found myself jammed into a 3 x 3 metre log cabin in almost pitch darkness with an 'owirúame' ¿ shaman ¿ and his three young helpers, and about a dozen members of the Guanapani family, three of whom were to be cured of vaarious ailments. The shaman whose name was Wenceslao Sinaloa looked like a North American Indian cowboy: dark, high cheekbones, straight stringy black hair topped by a cowboy hat. He wore a denim jacket and pants.

The shaman and two helpers very seriously went about their business. With tesguïno (a fermented alcoholic drink made from corn), candles, crucifixes, and a kind of flower they made the sign of the cross above, in front of, at the shoulders, and behind every one of the Guanapanis who were kneeling.

The ones who suffered from ailments were next made to drink a clear liquid that was some kind of a cactus juice, perhaps mixed with herbs. Mumbled prayers and incantations in Tarahumara accompanied the proceedings.

Now performing by himself, the shaman approached each member of the family. One by one, slowly, he felt a head there, a chest elsewhere. At times he would bend over and suck the skin of an arm, a forehead or a leg. Out he would spit what he called 'gusanos' ¿ worms ¿ into a gourd. This 'gusano' he showed me several times. It did indeed look like a worm floating in spittle. Each time the substance was then thrown into a small fire. Twice he spat out small pebbles.

The curing ceremony having finished for the Guanapanis, I ventured to tell Wenceslao Sinaloa that I had been suffering from a very strong, possibly rheumatic pain in my right arm for about three months. It was getting worse, I told him.

Wenceslao looked me straight in the eye for a moment ¿ I could feel his power ¿ then he started to feel my arm. He found the spot where the pain was most intense. Kneading the sore point briefly, he bent over and sucked the arm. Out came another little 'gusano'. He left no mark on the arm. "It will take a week before you are well," said Wenceslao Sinaloa.

During the next busy days I forgot all about the 'cure' and the intense pain persisted. Then ¿ suddenly one morning I woke up and realised that something was different. The pain was gone, totally gone! It was indeed the seventh day after Wenceslao Sinaloa sucked a 'gusano' out of my arm.

Said Padre Verplancken, the missionary priest, when I recouinted this to him: "They have kept their curings and customs and rituals exactly the way they were 300 years ago. Sometimes it works ¿ for some reason."