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.