“Good boy!  He certainly has nerve!” said Fred to himself, admiringly.  “He doesn’t know what’s going to happen to him next, but he is certainly doing all he can to make things come right.”

Then there was a new confusion of noise outside.  Fred heard Boris call Vladimir and speak to the old servant in Russian.  Then the German officer gave Vladimir his instructions.

“This place will be left alone for the present,” he said.  “Prince Alexander Suvaroff has been a good friend and neighbor, and, though he is an enemy, we desire to respect his property as long as possible.  But neither you nor any who are left in the house with you must go out—­this for your own safety—­except to get food and then go yourself.”

Fred heard a general movement then, and guessed that they were going out.  Silence followed, and, after listening for a time, he decided upon an exploration of the secret passage.  A vague plan was taking form in his mind already.  It seemed to him that, as he was at liberty, he should do anything that was in his power to free Boris.  Until he knew more of the lay of the land, he could not even make a real plan, but it was possible, he thought, that something that was in his mind might easily prove to be feasible.

It was easy, with his torch and the guiding arrows, to follow the devious, winding course of the passage.  He surmised that its ascents and descents, which seemed arbitrary and unreasonable as he pursued them, were due to other entrances than the one he knew.  It would be necessary, as he could understand, to have more than one means of getting in and out of such a passage.  And when he found himself at last going in a straight path which sloped easily downward, he guessed that he was beyond the house, and that he had come to a part of the passage that led to the outer world.

Here there was a trace of dampness, but nothing like what might have been expected in what was really a tunnel.  Fred had to admire the excellence of the construction work.  The descent, as he knew from what he had seen outside, must really be very sharp.  But it was managed here with turns and zigzags so that the grade was never very sharp.

Fred became suddenly conscious of a change in the air.

“I must be near the opening,” he thought.

A couple of minutes proved that he was right.  He now remembered that Boris had not had time to tell him how the door or gate was operated.  But he decided not to go back at once, but to try to discover the secret for himself.  It had occurred to him that it was more than probable that a sentry or two might be left in the house, and he had no mind to stay in the passageway, helpless and useless, if Vladimir found it impossible to let him out at once.

At the end of the passage he found a solid, seamless door.  He decided at once it must work on an axis of some sort and that it must be set in motion by pressing a spring.  And so, steadily and systematically, he searched the whole door, until he struck the right spot at last.  As the door moved, he marked the spot with a tiny pencil mark.  It swung open—­and he looked into the eyes of a startled German soldier, his mouth wide open!