He knew now for certain the cause of his uneasiness.
Some dreadful human being was very near to him, full of hateful thoughts, sinister recollections, possibly evil intentions.

Something, the very vibrations of the night air, it might be, carried, as a telegraph wire conveys a message, the soul-aroma of this human being to the doctor.

As he walked on, not hurrying, he mutely diagnosed the heart of this unseen being.

It seemed full of deadly disease.

Never had he suspected man or woman of such wickedness as he divined here; never had he felt from any of his kind such a sick repulsion as from this unseen monster who was journeying steadily in his steps.