She obeyed without hesitation.  Quest watched, for a moment, her regular breathing.  Then he touched a bell by his side.  Laura entered almost at once.

“Open the laboratory,” Quest ordered.  “Then come back.”

Without a word or a glance towards the sleeping figure, she obeyed him.  It was a matter of seconds before she returned.  Together they lifted and carried the sleeping girl out of the room, across the landing, into a larger apartment, the contents of which were wrapped in gloom and mystery.  A single electric light was burning on the top of a square mirror fixed upon an easel.  Towards this they carried the girl and laid her in an easy-chair almost opposite to it.

“The battery is just on the left,” Laura whispered.

Quest nodded.

“Give me the band.”

She turned away for a moment and disappeared in the shadows.  When she returned, she carried a curved band of flexible steel.  Quest took it from her, attached it by means of a coil of wire to the battery, and with firm, soft fingers slipped it on to Lenora’s forehead.  Then he stepped back.  A rare emotion quivered in his tone.

“She’s a subject, Laura—­I’m sure of it!  Now for our great experiment!”

They watched Lenora intently.  Her face twitched uneasily, but she did not open her eyes and her breathing continued regular.  Quest bent over her.

“Lenora,” he said, slowly and firmly, “your mind is full of one subject.  You see your mistress in her chair by the fireside.  She is toying with her diamonds.  Look again.  She lies there dead!  Who was it entered the room, Lenora?  Look!  Look!  Gaze into that mirror.  What do you see there?”

The girl’s eyes had opened.  They were fixed now upon the mirror—­distended, full of unholy things.  Quest wiped a drop of perspiration from his forehead.

“Try harder, Lenora,” he muttered, his own breath labouring.  “It is there in your brain!  Look!”

Laura for the first time showed signs of emotion.  She pointed towards the mirror.  Quest was suddenly silent.  He seemed to have turned into a figure of stone.  For a single second the smooth surface of the mirror was obscured.  A room crept dimly like a picture into being, a fire upon the hearth, a girl leaning back in her chair.  A door in the background opened.  A man stole out.  He crept nearer to the girl—­his eyes fixed upon the diamonds, a thin, silken cord twisted round his wrist.  Suddenly she saw him—­too late!  His hand was upon her lips,—­his face seemed to start almost from the mirror—­then blackness!

* * * * *

Lenora opened her eyes.  She was still in the easy-chair before the fire.

“Mr. Quest!” she faltered.

He looked up from some letters which he had been studying.

“I am so sorry,” he said politely.  “I really had forgotten that you were here.  But you know—­that you have been to sleep?”