“What were you doing by the fire before you came here?” he asked, pausing, in a casual tone, as he lit a cigarette and handed the case to his patient.

“I?  Let me see.  Oh, I know; I was worrying my way through poor old Ebor’s papers and things.  I’m his executor, you know.  Then I got weary and came out for a whiff of air.”  He spoke lightly and with perfect naturalness.  Obviously he was telling the truth.  “I prefer specimens to papers,” he laughed cheerily.

“I know, I know,” said Dr. Stephen, holding a lighted match for the cigarette.  His face wore an expression of content.  The experiment had been a complete success.  The memory of the last two hours was wiped out utterly.  Laidlaw was already chatting gaily and easily about a dozen other things that interested him.  Together they went out into the street, and at his door Dr. Stephen left him with a joke and a wry face that made his friend laugh heartily.

“Don’t dine on the professor’s old papers by mistake,” he cried, as he vanished down the street.

Dr. Laidlaw went up to his study at the top of the house.  Half way down he met his housekeeper, Mrs. Fewings.  She was flustered and excited, and her face was very red and perspiring.

“There’ve been burglars here,” she cried excitedly, “or something funny!  All your things is just any’ow, sir.  I found everything all about everywhere!” She was very confused.  In this orderly and very precise establishment it was unusual to find a thing out of place.

“Oh, my specimens!” cried the doctor, dashing up the rest of the stairs at top speed.  “Have they been touched or—­”

He flew to the door of the laboratory.  Mrs. Fewings panted up heavily behind him.

“The labatry ain’t been touched,” she explained, breathlessly, “but they smashed the libry clock and they’ve ’ung your gold watch, sir, on the skelinton’s hands.  And the books that weren’t no value they flung out er the window just like so much rubbish.  They must have been wild drunk, Dr. Laidlaw, sir!”

The young scientist made a hurried examination of the rooms.  Nothing of value was missing.  He began to wonder what kind of burglars they were.  He looked up sharply at Mrs. Fewings standing in the doorway.  For a moment he seemed to cast about in his mind for something.

“Odd,” he said at length.  “I only left here an hour ago and everything was all right then.”

“Was it, sir?  Yes, sir.”  She glanced sharply at him.  Her room looked out upon the courtyard, and she must have seen the books come crashing down, and also have heard her master leave the house a few minutes later.

“And what’s this rubbish the brutes have left?” he cried, taking up two slabs of worn gray stone, on the writing-table.  “Bath brick, or something, I do declare.”

He looked very sharply again at the confused and troubled housekeeper.

“Throw them on the dust heap, Mrs. Fewings, and—­and let me know if anything is missing in the house, and I will notify the police this evening.”