He stopped abruptly, as if sorry he had said so much, and a moment later the party were walking in Indian file through the turnstile, Sir John Burney leading the way.

Mrs. Bunting looked straight before her.  She felt—­so she expressed it to her husband later—­as if she had been turned to stone.

Even had she wished to do so, she had neither the time nor the power to warn her lodger of his danger, for Daisy and her companion were now coming down the room, bearing straight for the Commissioner of Police.  In another moment Mrs. Bunting’s lodger and Sir John Burney were face to face.

Mr. Sleuth swerved to one side; there came a terrible change over his pale, narrow face; it became discomposed, livid with rage and terror.

But, to Mrs. Bunting’s relief—­yes, to her inexpressible relief —­Sir John Burney and his friends swept on.  They passed Mr. Sleuth and the girl by his side, unaware, or so it seemed to her, that there was anyone else in the room but themselves.

“Hurry up, Mrs. Bunting,” said the turnstile-keeper; “you and your friends will have the place all to yourselves for a bit.”  From an official he had become a man, and it was the man in Mr. Hopkins that gallantly addressed pretty Daisy Bunting:  “It seems strange that a young lady like you should want to go in and see all those ’orrible frights,” he said jestingly.

“Mrs. Bunting, may I trouble you to come over here for a moment?”

The words were hissed rather than spoken by Mr. Sleuth’s lips.

His landlady took a doubtful step towards him.

“A last word with you, Mrs. Bunting.”  The lodger’s face was still distorted with fear and passion.  “Do not think to escape the consequences of your hideous treachery.  I trusted you, Mrs. Bunting, and you betrayed me!  Put I am protected by a higher power, for I still have much to do.”  Then, his voice sinking to a whisper, he hissed out “Your end will be bitter as wormwood and sharp as a two-edged sword.  Your feet shall go down to death, and your steps take hold on hell.”

Even while Mr. Sleuth was muttering these strange, dreadful words, he was looking round, glancing this way and that, seeking a way of escape.

At last his eyes became fixed on a small placard placed above a curtain.  “Emergency Exit” was written there.  Mrs. Bunting thought he was going to make a dash for the place; but Mr. Sleuth did something very different.  Leaving his landlady’s side, he walked over to the turnstile, he fumbled in his pocket for a moment, and then touched the man on the arm.  “I feel ill,” he said, speaking very rapidly; “very ill indeed!  It is the atmosphere of this place.  I want you to let me out by the quickest way.  It would be a pity for me to faint here—­especially with ladies about.”

His left hand shot out and placed what he had been fumbling for in his pocket on the other’s bare palm.  “I see there’s an emergency exit over there.  Would it be possible for me to get out that way?”