Kennedy and I were not the only visitors to the subterranean chamber where it had seemed that the clue to the Clutching Hand’s millions might be found.

It was as though that hidden, watching eye followed us.  The night after our own unsuccessful search, Wu Fang, accompanied by Long Sin, made his way into the cavern.

As they flashed their electric bull’s-eyes about the place, they could see readily that we had already been digging there.

Wu examined the safe which had been broken into, while Long Sin repeated his experiences there.

“And you say there was nothing else in it?” demanded Wu.

“Nothing but the ring which they got from me,” replied Long Sin, ruefully.

“Strange—­very strange,” ruminated Wu, still regarding the empty strong box.

Long Sin was now going over the walls of the cavern minutely, his close-set, beady black eyes examining every square inch of it.

A sudden low guttural exclamation caused Wu to turn to him quickly.  Long Sin had discovered, back of the debris, a small oblong slot, cut into the rock.  Above it were some peculiar marks.

Wu hurried over to his henchman, and together they tried to decipher what had been scratched on the rock.

As Long Sin’s slender and sinister forefinger traced over the inscription, Wu suddenly caught him by the elbow.

“The ring!” he cried, as at last he interpreted the meaning of the cryptic characters.

But what about the ring?  For a moment Wu looked at the slot in deep thought.  Then he reached down and withdrew a ring from his own finger and dropped it through the slot.

They listened a moment.  They could hear the ring tinkle as though it were running down some sort of track-like declivity inside the rock.  Then, faintly, they could hear it drop.  It had fallen into a little cup of a compartment below at their feet.

Nothing happened.  Wu recovered his ring.  But he had hit at last upon the Clutching Hand’s secret!

Bennett had devised a ring-lock which would open, the treasure vault.  No other ring except the one which he had so carefully hidden was of the size or weight that would move the lever which would set the machinery working to open the treasure house.

Again Wu tried another of his own rings, and a third time Long Sin dropped in a ring from his finger.  Still there was no result.

“The ring which we lost is the key to the puzzle—­the only key,” exclaimed Wu Fang finally.  “We must recover it at all hazard.”

To his subtle mind a plan of action seemed to unfold almost instantly.  “There is no good remaining here,” he added.  “And we have gained nothing by the capture of the girl, unless we can use her to recover the ring.”

Long Sin followed his master with a sort of intuition.  “If we have to steal it,” he suggested deferentially, “it can be accomplished best by making use of Chong Wah Tong.”