There's this cave full of vampire bats, roosting.
A solitary bat flutters into the cave and heads for his perch. He's just wrapping himself up snugly, when his neighbour starts sniffing.
"Blood ... ?"
In no time, the cave is in an uproar, all the bats swarming around the latecomer.
"Blood! We smell blood! Where did you get the blood!?"
The solitary bat, who does indeed smell of blood, just mumbles through his wings.
"Le'me in peace. I jus' wanna sleep."
But the others are unrelenting.
"No! No! You found blood! You've got to share! Show us where the blood is!"
In the end the solitary bat has to give up.
"Okay. Fine. I'll show you the blood."
A cloud of vampire bats swarms out of the cave, the solitary one leading them. They head down the valley, across the moonlit lake, and into the dark forest. After a while they end up in a clearing in the forest, with a gigantic tree standing in the middle. The solitary bats says:
"You all see that tree?"
"Yes! Yes!", they go ("Blood! Blood!")
"Fine," he says, "I didn't."