引狼入室 — “Lead a wolf into one's house”

There was a shepherd grazing his flock in a valley. He saw a wolf following from a distance and remained constantly on guard.

Several months passed, and the wolf only followed from afar, never approaching the sheep nor harming any. The shepherd gradually lowered his guard.

Later, the shepherd even thought it was beneficial to have the wolf behind the flock, as he no longer needed to worry about other wild beasts. Eventually, he simply treated the wolf as a sheepdog and entrusted it with guarding the flock.

Seeing the wolf manage the sheep so well, the shepherd thought to himself, 'Everyone says wolves are the worst, but I don't see it that way...'

One day, the shepherd had to go into town for something and left the sheep in the wolf's care. The wolf agreed. Once the wolf estimated the shepherd had entered the town, it let out several loud howls towards the forest. Its howls attracted many, many wolves of all sizes. The entire flock of sheep was devoured by the wolves.

The shepherd did not understand the wolf's true nature and was deceived by its false kindness.

The idiom '引狼入室' (yǐn láng rù shì) metaphorically refers to bringing bad people or enemies into one's inner circle.