The Cat, the Mouse and the Cheese

The Cat, the Mouse and the Cheese. There was a man who had a big, beautiful chunk of cheese which he kept in a box, but a mouse was eating the cheese. Following his friend's advice, he put a cat in the box but after killing the mouse, the cat ate up all the cheese.
Moral: The story shows that you shouldn't employ guardians who are able to do as much harm as your enemies.

Caseus, Mus et Feles. Vir quidam magnum ac pulcherrimum in capsa caseum habebat, quem musculus edebat. Ex consilio ergo amici, felem illuc clausit quae, occiso mure, totum caseum comedit.
Morale. Fabula indicat eos non adhibendos custodes, qui non minus quam hostes nobis nocere possunt.

Notes. This is Abstemius 116. You can find a similar version in Odo of Cheriton 21. Perry does not include many of Abstemius's fables in his classification system, but he does include a large number of fables from Odo, so this story does have a Perry number; it's Perry 594.