“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 passed.  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.