“Indeed,” said Thorndyke.  “I wonder if he still has the same housekeeper.”

“This lady is a German,” replied the clerk, “with a regular jaw-twisting name.  Sounded like Shallybang.”

“Schallibaum.  That is the lady.  A fair woman with hardly any eyebrows and a pronounced cast in the left eye.”

“Now that’s very curious, sir,” said the clerk.  “It’s the same name, and this is a fair woman with remarkably thin eyebrows, I remember, now that you mention it But it can’t be the same person.  I have only seen her a few times and then only just for a minute or so; but I’m quite certain she had no cast in her eye.  So, you see, sir, she can’t be the same person.  You can dye your hair or you can wear a wig or you can paint your face; but a squint is a squint.  There’s no faking a swivel eye.”

Thorndyke laughed softly.  “I suppose not; unless, perhaps, some one might invent an adjustable glass eye.  Are these the keys?”

“Yes, sir.  The large one belongs to the wicket in the front gate.  The other is the latch-key belonging to the side door.  Mrs. Shallybang has the key of the front door.”

“Thank you,” said Thorndyke.  He took the keys, to which a wooden label was attached, and we made our way back towards the house of mystery, discussing the clerk’s statements as we went.

“A very communicable young gentleman, that,” Thorndyke remarked.  “He seemed quite pleased to relieve the monotony of office work with a little conversation.  And I am sure I was very delighted to indulge him.”

“He hadn’t much to tell, all the same,” said I.

Thorndyke looked at me in surprise.  “I don’t know what you would have, Jervis, unless you expect casual strangers to present you with a ready-made body of evidence, fully classified, with all the inferences and implications stated.  It seemed to me that he was a highly instructive young man.”

“What did you learn from him?” I asked.

“Oh, come, Jervis,” he protested; “is that a fair question, under our present arrangement?  However, I will mention a few points.  We learn that about six or seven months ago, Mr. H. Weiss dropped from the clouds into Kennington Lane and that he has now ascended from Kennington Lane into the clouds.  That is a useful piece of information.  Then we learn that Mrs. Schallibaum has remained in England; which might be of little importance if it were not for a very interesting corollary that it suggests.”

“What is that?”

“I must leave you to consider the facts at your leisure; but you will have noticed the ostensible reason for her remaining behind.  She is engaged in puttying up the one gaping joint in their armour.  One of them has been indiscreet enough to give this address to some correspondent—­probably a foreign correspondent.  Now, as they obviously wish to leave no tracks, they cannot give their new address to the Post Office to have their letters forwarded, and, on the other hand, a letter left in the box might establish such a connection as would enable them to be traced.  Moreover, the letter might be of a kind that they would not wish to fall into the wrong hands.  They would not have given this address excepting under some peculiar circumstances.”