"Another danger!" exclaimed Duncan. "My uncle was right. I read his letters, Abdul, in the room upstairs. He said that Isaac Coffran was a fiend!
"I understand it all, now. He murders a man by gas, in the upstairs room. The body is brought down the lift. It is drawn to the floor, the trap is released and down goes the victim!
"He has discovered my escape, Abdul. He knows that some one has helped me. From some room upstairs he operates his hidden mechanisms. He dropped the curtain of steel. He brought the elevator up again. He released the catches that hold the trap, hoping that one or both of us might fall into some pit below. He has us here, at his mercy. What will he do next?"
"We must wait to see, burra sahib," said the Hindu quietly.
Duncan moved cautiously to the steel curtain. He tapped against it with a key. The click seemed loud in the darkness.
There was an answering sound — a faint echo of the click. Yet it brought a sudden hope to Bruce Duncan.
He stepped closer and tapped three times. Three clicks replied.
Using the International code, Duncan slowly spelled out a single word: "Help."
The reply came: "Who are you?"
"It may be a friend, Abdul," exclaimed Duncan in a low tone. "He wants to know who is here."