“Listen!” said Valerie. “All the men in camp here have gone off to Minden Plains, which are back of Pedisgill Hill, to practise some special manœuver—all except the man at the door here, and five men who are at work in Big Bear Gap, which is almost at the other end of the valley. They are at work on some air-ships there and the ‘Black Hawk’ is keeping an eye over them.”

“Yes, yes,” assented the Professor, “but how are we going to get out of here?”

“When I next return,” said Valerie, “you will seize and bind me securely with one of these cords, which for all anybody will know you found by ransacking the cabin.”

“But how shall we deal with the sentry outside?” questioned the Professor.

“Oh, that will be simple enough,” replied Valerie. “Jack is on guard and Jack will do anything I say, even though it were to send a bullet through the ‘Black Hawk’ himself. After you have secured me, you will give three light taps upon the door. Jack won’t be very much surprised when he opens the door if you suddenly pounce upon him and secure him in the same way that you do me. You are two to one and his capture need not create suspicion. He will struggle, of course, just to keep up appearances, but don’t hurt the poor boy, since he is really our friend.”

“I don’t like the plan,” broke in Mortimer, speaking for the first time, “since it involves violence—or rather the appearance of violence—to you. I would much rather you were not mixed up in this—much rather that it were managed by that fellow Henry coming here, or someone else.”

“Don’t be silly!” exclaimed Valerie. “It’s the kindest thing you can do for me, since it will serve to divert suspicion far more than any other plan.”

“Still, I don’t like it,” retorted Mortimer obstinately. “I would give almost anything I possess to escape from here, but I don’t like your being involved.”

“I’m bound,” said Valerie, determinedly, “that you shall not remain behind at the mercy of the ‘Black Hawk.’ You’ve got to escape. But,” she added, her manner softening, “you’ll promise me that after you are safely away, you will never bring anything here that will do injury to me or mine—to the men of this camp?”

“Should I ever succeed in escaping,” answered Mortimer solemnly, “I’ll promise never to disclose the situation of this valley, or to lead, or direct, any attacking force here. More than this I can’t promise.”