--tap--tap--tap--tap--tap--tap. Instinctively her hand went out,
groping along the wall until it fell upon a pipe. Even as she touched
this the sound came again, and along with it the faintest of vibrations.
She knew that somebody at a distance was hitting the pipe with a piece
of quartz or metal.

Stooping, she found a bit of broken rock. Three times she tapped the
pipe. An answer came at once.

Tap--tap--tap--tap--tap--tap--tap!

She tried two knocks. Again the response of seven taps sounded. Four
blows brought still seven. Why always seven? She did not know, but she
was greatly comforted to know that her friends were in communication
with her. After all she was not alone.

A light glimmered at the end of the tunnel and moved slowly toward her.
Bleyer's voice called her name. Presently the whole party was about her
with sympathetic questions and explanations.

She made light of her fainting attack, but Verinder insisted on getting
her back to the upper air in spite of her protests. He had discovered
that Joyce was quite ready to return to the sunlight, now that her
curiosity was satisfied. A very little of anything that was unpleasant
went a long way with Miss Seldon, and there was something about this
underground tomb that reminded her strongly of an immense grave.

At dinner Verinder referred to the attack of vertigo. "Feel quite fit
again, Miss Dwight?"

"Quite, thank you." Moya was a little irritated at the reference,
because she was ashamed of having given way to physical weakness. "It
was nothing. I was a goose. That's all."

Bleyer, a guest for the evening, defended the young woman from her own
scorn. "It often takes people that way the first time, what with the
heat and the closeness. I once knew a champion pugilist to keel over
while he was going through a mine."

"Were you afraid when you found yourself alone?" Joyce asked.

"I was until you tapped."

India looked puzzled. "Tapped. What do you mean?"

"On the pipe."

"What pipe?"

"The one that ran through the tunnel."

Miss Kilmeny shook her head. "I didn't see anybody tap. Perhaps one of
us touched it by chance."

"No. That couldn't be. The tap came seven times together, and after I
had answered it seven times more."

"Seven times?" asked Bleyer quickly.

"Yes--seven. But, if you didn't tap, who did?"

"Sure it wasn't imagination?" Verinder suggested.

"Imagination! I tell you it was repeated again and again," Moya said
impatient