What is unusual about the visitor who comes to holmes apartments

Explanation:

When Holmes and Watson returned to the house, Watson laid down to take a nap as his mind was tumultuous after the events of the morning. He meditated on the grotesque visage of the dead man and almost thanked the murderer for ridding the world of such a clearly malignant man. Of course, he did recognize that "justice must be done, and that the depravity of the victim was no condonement in the eyes of the law."

im not to sure