[Ill.u.s.tration: SANFORD QUEST IS CALLED UPON TO CLEAR THE MYSTERY OF THE MURDER OF LORD ASHLEIGH'S DAUGHTER.]

[Ill.u.s.tration: UNDER THE HYPNOTIC INFLUENCE OF QUEST, LENORA REVEALS THE STRANGE DISAPPEARANCE OF THE JEWELS, AND THE MURDER.]

"I may go now, then?" she repeated, with immense relief.

Quest escorted the girl downstairs, opened the front door, blew his whistle and his car pulled up at the door.

"Take this young lady," he ordered, "wherever she wishes. Good night!"

The girl drove off. Quest watched the car disappear around the corner.

Then he turned slowly back and made preparations for his adventure....

"Number 700, New York," he muttered, half an hour later, as he left his house. "Beyond Fourteenth Street--a tough neighbourhood."

He hesitated for a moment, feeling the articles in his overcoat pocket--a revolver in one, a small piece of hard substance in the other. Then he stepped into his car, which had just returned.

"Where did you leave the young lady?" he asked the chauffeur.

"In Broadway, sir. She left me and boarded a cross-town car."

Quest nodded approvingly.

"No finesse," he sighed.

5.

Sanford Quest was naturally a person unaffected by presentiments or nervous fears of any sort, yet, having advanced a couple of yards along the hallway of the house which he had just entered without difficulty, he came to a standstill, oppressed with the sense of impending danger. With his electric torch he carefully surveyed the dilapidated staircase in front of him, the walls from which the paper hung down in depressing-looking strips. The house was, to all appearances, uninhabited.

The door had yielded easily to his master-key. Yet this was the house connected with Number 700, New York, the house to which Lenora had come.

Furthermore, from the street outside he had seen a light upon the first floor, instantly extinguished as he had climbed the steps.

"Any one here?" he asked, raising his voice a little.

There was no direct response, yet from somewhere upstairs he heard the half smothered cry of a woman. He gripped his revolver in his fingers. He was a fatalist, and although for a moment he regretted having come single-handed to such an obvious trap, he prepared for his task. He took a quick step forward. The ground seemed to slip from beneath his feet. He staggered wildly to recover himself, and failed. The floor had given from beneath him. He was falling into blackness....

The fall itself was scarcely a dozen feet. He picked himself up, his shoulder bruised, his head swimming a little. His electric torch was broken to pieces upon the stone floor. He was simply in a black gulf of darkness. Suddenly a gleam of light shone down. A trap-door above his head was slid a few inches back. The flare of an electric torch shone upon his face, a man's mocking voice addressed him.

"Not the great Sanford Quest? This surely cannot be the greatest detective in the world walking so easily into the spider's web!"

"Any chance of getting out?" Quest asked laconically.

"None!" was the bitter reply. "You've done enough mischief. You're there to rot!"

"Why this animus against me, my friend Macdougal?" Quest demanded. "You and I have never come up against one another before. I didn't like the life you led in New York ten years ago, or your friends, but you've suffered nothing through me."

"If I let you go," once more came the man's voice, "I know very well in what chair I shall be sitting before a month has pa.s.sed. I am James Macdougal, Mr. Sanford Quest, and I have got the Ashleigh diamonds, and I have settled an old grudge, if not of my own, of one greater than you.

That's all. A pleasant night to you!"

The door went down with a bang. Faintly, as though, indeed, the footsteps belonged to some other world, Sanford Quest heard the two leave the house.

Then silence.

"A perfect oubliette," he remarked to himself, as he held a match over his head a moment or two later, "built for the purpose. It must be the house we failed to find which Bill Taylor used to keep before he was shot.

Smooth brick walls, smooth brick floor, only exit twelve feet above one's head. Human means, apparently, are useless. Science, you have been my mistress all my days. You must save my life now or lose an earnest disciple."

He felt in his overcoat pocket and drew out the small, hard pellet. He gripped it in his fingers, stood as nearly as possible underneath the spot from which he had been projected, coolly swung his arm back, and flung the black pebble against the sliding door. The explosion which followed shook the very ground under his feet. The walls cracked about him. Blue fire seemed to be playing around the blackness. He jumped on one side, barely in time to escape a shower of bricks. For minutes afterwards everything around him seemed to rock. He struck another match. The whole of the roof of the place was gone. By building a few bricks together, he was easily able to climb high enough to swing himself on to the fragments of the hallway. Even as he accomplished this, the door was thrown open and a crowd of people rushed in. Sanford Quest emerged, dusty but unhurt, and touched a constable on his arm.

"Arrest me," he ordered. "I am Sanford Quest. I must be taken at once to headquarters."

"That so, Mr. Quest? Stand on one side, you loafers," the man ordered, pushing his way out.

"We'll have a taxicab," Quest decided.

"Is there any one else in the house?" the policeman asked.

"Not a soul," Quest answered.

They found a cab without much difficulty. It was five o'clock when they reached the central police-station. Inspector French happened to be just going off duty. He recognized Quest with a little exclamation.

"Got your man to bring me here," Quest explained, "so as to get away from the mob."

"Say, you've been in trouble!" the Inspector remarked, leading the way into his room.

"Bit of an explosion, that's all," Quest replied. "I shall be all right when you've lent me a clothes-brush."

"The Ashleigh diamonds, eh?" the Inspector asked eagerly.

"I shall have them at nine o'clock this morning," Sanford Quest promised, "and hand you over the murderer somewhere around midnight."

The Inspector scratched his chin.

"From what I can hear about the young lady's friends," he said, "it's the murderer they are most anxious to see nabbed."

"They'll have him," Quest promised. "Come round about half-past nine and I'll hand over the diamonds to start with."

Quest slept for a couple of hours, had a bath and made a leisurely toilet.

At a quarter to nine he sat down to breakfast in his rooms.

"At nine o'clock," he told his servant, "a young lady will call. Bring her up."

The door was suddenly opened. Lenora walked in. Quest glanced in surprise at the clock.

"My fault!" he exclaimed. "We are slow. Good morning, Miss Lenora!"

She came straight to the table. The servant, at a sign from Quest, disappeared. There were black rims around her eyes; she seemed exhausted.

She laid a little packet upon the table. Quest opened it coolly. The Ashleigh diamonds flashed up at him. He led Lenora to a chair and rang the bell.

"Prepare a bedroom upstairs," he ordered. "Ask Miss Roche to come here.

Laura," he added, as his secretary entered, "will you look after this young lady? She is in a state of nervous exhaustion."