Lady was slinking out into the hall; crestfallen and scared.

The Master collared her and brought her back to the scene of her mischief.
The collie had disobeyed him.

Flagrantly she had sinned in assailing the bird; after his injunction of "Let it alone!" There could be no doubt, from her wriggling aspect of guilt, that she knew she was doing wrong.

Worse, she had taken sneaky advantage of his absence in order to spring at the eagle.

And disgust warred with the Master's normal indignation.
Speaking as quietly as he could bring himself to speak, he told Lady what she had done and what a rotten thing it had been.