There once was a shepherd boy who had the job of tending to the sheep that belonged to a village. He was watching over the sheep as they grazed in a clearing in a forest when a great pack of wolves appeared out of the forest and began chasing the sheep and scattering them. The boy cried “Wolves, wolves!” and all the villagers ran away because they were frightened.
"Don't cry 'wolf', shepherd boy," said the villagers after they straggled back to their village, "You frighten people with talk like that!"
A few days later, the wolves returned and the boy cried out again, "Wolves! Wolves! The wolves are chasing the sheep!" The villagers again ran away, leaving him alone to protect the sheep as best he could.
“We told you not to frighten us with these stories of wolves,” said the villagers. “We don’t believe you. We don’t think you ever saw any wolves.” From then on, they simply ignored the boy when he sounded the warning about wolves; they did not run away, but neither did they come to help him protect the sheep.
The wolves grew ever bolder, seeing that they had to contend with only one small boy. One day they summoned all the wolf packs from the surrounding countryside to join them in a gigantic raid on the flock. They dragged all the sheep off into the woods to eat at their leisure. They killed the shepherd boy and took his body along with them as well.
After a while the people of the village began to grow hungry for mutton, so they set out to bring home a sheep from the flock. When they got to the clearing in the forest, they found no sheep and no shepherd boy. “Look at this,” they told each other. “That thieving little boy has gone away and taken all our sheep with him. Now we know why he was crying ‘Wolf’ all the time. He was setting up his alibi.”
The moral of the story: Truth is precious. Don’t tell it too often, or nobody will believe you.