“Police, sir?” asked the man civilly.

“Yes,” said Smith; “hurry!”

Off went our guide without further demur.  Skirting sculleries, kitchens, laundries and engine-rooms, he led us through those mysterious labyrinths which have no existence for the guest above, but which contain the machinery that renders these modern khans the Aladdin’s palaces they are.  On a second-floor landing we met a man in a tweed suit, to whom our cicerone presented us.

“Glad I met you, sir.  Two gentlemen from the police.”

The man regarded us haughtily with a suspicious smile.

“Who are you?” he asked.  “You’re not from Scotland Yard, at any rate!”

Smith pulled out a card and thrust it into the speaker’s hand.

“If you are the hotel detective,” he said, “take us without delay to Mr. Graham Guthrie.”

A marked change took place in the other’s demeanor on glancing at the card in his hand.

“Excuse me, sir,” he said deferentially, “but, of course, I didn’t know who I was speaking to.  We all have instructions to give you every assistance.”

“Is Mr. Guthrie in his room?”

“He’s been in his room for some time, sir.  You will want to get there without being seen?  This way.  We can join the lift on the third floor.”

Off we went again, with our new guide.  In the lift: 

“Have you noticed anything suspicious about the place to-night?” asked Smith.

“I have!” was the startling reply.  “That accounts for your finding me where you did.  My usual post is in the lobby.  But about eleven o’clock, when the theater people began to come in I had a hazy sort of impression that someone or something slipped past in the crowd—­something that had no business in the hotel.”

We got out of the lift.

“I don’t quite follow you,” said Smith.  “If you thought you saw something entering, you must have formed a more or less definite impression regarding it.”

“That’s the funny part of the business,” answered the man doggedly.  “I didn’t!  But as I stood at the top of the stairs I could have sworn that there was something crawling up behind a party—­ two ladies and two gentlemen.”

“A dog, for instance?”

“It didn’t strike me as being a dog, sir.  Anyway, when the party passed me, there was nothing there.  Mind you, whatever it was, it hadn’t come in by the front.  I have made inquiries everywhere, but without result.”  He stopped abruptly.  “No. 189—­Mr. Guthrie’s door, sir.”

Smith knocked.

“Hallo!” came a muffled voice; “what do you want?”

“Open the door!  Don’t delay; it is important.”

He turned to the hotel detective.

“Stay right there where you can watch the stairs and the lift,” he instructed; “and note everyone and everything that passes this door.  But whatever you see or hear, do nothing without my orders.”