They walked down Praed Street without adventure, and Mr. Ludgrove unlocked the door of his shop with his latchkey. They passed through it into the inner room, the window of which was already curtained and the gas lighted. Dr. Priestley cast a swift glance round it, noting with interest the scientific instruments on the bench, the cases full of books, and two comfortable armchairs. “This is a very comfortable room of yours, Mr. Ludgrove,” he remarked approvingly.

“It has heard some queer stories in its time,” replied Mr. Ludgrove with a smile. “You can form no idea of the extraordinary confessions which some of my clients force me to listen to. But I can assure you that it has heard nothing more amazing that the story which I am about to unfold to you this evening.”

“May I ask a question before you begin, Mr. Ludgrove?” said the Professor quietly.