Seizing the hammer, Coucon struck three hard blows on the walls at regular intervals. He waited and listened. Three blows answered him. He struck again, varying the number, which were immediately repeated.
"Yes, it is plain. Our friends hear us, and wish to communicate with us. But hark! they have begun." Twenty-five blows were struck, one after the other, in quick succession. The three looked at each other, greatly troubled.
"The twenty-five letters of the alphabet!" cried Madame.
"Yes," said Carmen, "repeat, to prove that you understand."
After repeated experiments it was found that communication was easy, and Carmen spelled out:
"There is an iron door under the silk."
"I knew it!" Coucon exclaimed, "I had began to tear it off when you came."
They pulled off the silk, and suddenly Coucon exclaimed:
"Here is the door!" Without well knowing what he was doing, Coucon pressed the knob, and the panel flew open so quickly that Coucon was nearly knocked over. "Take the light and come!" he shouted.