Ferguson sat up with a cry of joy.

“Prove that, Mr. Holmes, and I am your debtor forever.”

“I will do so, but in doing so I must wound you deeply in another direction.”

“I care nothing so long as you clear my wife. Everything on earth is insignificant compared to that.”

“Let me tell you, then, the train of reasoning which passed through my mind in Baker Street. The idea of a vampire was to me absurd. Such things do not happen in criminal practice in England. And yet your observation was precise. You had seen the lady rise from beside the child’s cot with the blood upon her lips.”

“I did.”