There lived a skinny wolf who could not get enough to eat because of the watchfulness of the shepherds. One night he found a sheep skin that had been cast aside and forgotten. The next day, dressed in the skin, the wolf strolled into the pasture with the sheep. The shepherd was sitting in the feild leaving the sheep grazing. The wolf dressed in the skin of sheep followed the flock of sheep but did not harm them. After a few days, the shepherd saw that only few sheep were left and only one sheep has turned fatty. When he noticed properly, he found the wolf under the skin of sheep then the shepherdtook a knife and killed the wolf. 
the evil doer often comes to harm through his own deceit. 