"'He may be a lawyer, a merchant, a Doctor...'" she chanted ominously to herself.
Miss Cornelia, too, was not entirely at ease.
"In the center of this ring of light," she proceeded, her eyes on the Doctor's calm countenance, "was an almost perfect silhouette of a bat." "A bat!" The Doctor seemed at sea.

"Ah, I see--the symbol of the criminal of that name." He laughed again.
"I think I can explain what you saw.

Quite often my headlights collect insects at night and a large moth, spread on the glass, would give precisely the effect you speak of.

Just to satisfy you, I'll go out and take a look." He turned to do so.

Then he caught sight of the raincoat-covered huddle on the floor.
"Why--" he said in a voice that mingled astonishment with horror.