There was a wolf who dressed as a shepherd, wearing a shepherd's cloak and carrying a shepherd's crook.
He wore the costume so well that the people were fooled, as were the sheep and even the dogs. By pretending to keep the sheep, he was able to poach them, one after another, and he grew fatter and fatter.
One night, in his excitement, he made the mistake of letting out a cry of joy: the howl of a wolf, not a shepherd.
At that moment, all the shepherds and dogs realized his true identity, and they caught and killed him.
Inspired by: Fables of Aesop and Other Eminent Mythologists by Roger L'Estrange, 395.
Notes: This fable is not part of the classical Aesop tradition; find out more here.
Here is an illustration by Billinghurst: