Why did everybody in the village think Mark would die?

Mark was a farmer who lived in a village far away. One day he became very ill and everybody thought he would die. They sent for a doctor in town, who arrived two days later and examined the sickman. The doctor asked for a pen and some paper to write down the name of the medicine. But there was no pen or paper in the village, because no one could read or write.
    The doctor picked up a piece of burnt wood from the fire. Using the wood, he wrote the name of the medicine on the door of the house. "Get this medicine for him," he said, "and he will soon get better."
    Mark’s family and friends did not know what to do. They could not read the strange writing. Then the village baker had an idea. He took off the door of the house, put it on his cart and drove to the nearest town. he bought the medicine, and Mark was soon well again. He would not let anyone wash the magic words from the door.