A vampire bat came flapping in from the night covered in fresh blood and parked himself on the roof of the cave to get some sleep.

Pretty soon all the other bats smelt the blood and began hassling him about where he got it. He told them to go away and let him get some sleep. However, the bats persisted until finally he gave in.

"OK, follow me," he said and flew out of the cave with hundreds of bats behind him. Down through a valley they went, across a river and into a forest full of trees. Finally he slowed down and all the other bats excitedly milled around him.

"Now, do you see that tree over there?" he asked.

"Yes, yes, yes!" the bats all screamed in a hungry frenzy.

"Good," said the first bat tiredly, "Because I didn't!"