The man hesitated. It was evident that he regretted the temerity
that had made him the centre of interested observation. But at
last, seeing no alternative, he spoke.

"It might be tampered with," he said, "by an enemy."

Carthoris drew a small key from his leathern pocket-pouch.

"Look at this," he said, handing it to the man. "If you know aught
of locks, you will know that the mechanism which this unlooses is
beyond the cunning of a picker of locks. It guards the vitals of
the instrument from crafty tampering. Without it an enemy must
half wreck the device to reach its heart, leaving his handiwork
apparent to the most casual observer."

The servant took the key, glanced at it shrewdly, and then as he
made to return it to Carthoris dropped it upon the marble flagging.
Turning to look for it he planted the sole of his sandal full upon
the glittering object. For an instant he bore all his weight upon
the foot that covered the key, then he stepped back and with an
exclamation as of pleasure that he had found it, stooped, recovered
it, and returned it to the Heliumite. Then he dropped back to his
station behind the nobles and was forgotten.

A moment later Carthoris had made his adieux to Thuvan Dihn and
his nobles, and with lights twinkling had risen into the star-shot
void of the Martian night.