"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!