is engine.

As silent as a shadow the boat slid forward. Suddenly Roy detected
what he was looking for. At the same moment a high bank loomed up
directly before them. The craft ahead turned toward the right and
slipped along the narrowing channel. A few yards further on, it came
to rest, its nose lying softly against the muddy shore. Before it the
steep bank led upward to an open, level space that both Roy and Henry
felt instinctively was a public highway; for on either hand, though at
many rods' distance, could be seen the glow of a lamp that was
invisible itself.

The scout boat also came to rest, its momentum overcome by the
resistance of the water. Like a shadow it lay, not more than fifty
yards from the waiting spy craft. Crouching low behind the gunwale,
its four occupants held their breath as they watched the party in the
boat ahead. Assisted by the faint glow of the distant street lamps,
they could vaguely make out the forms of their quarry; while the
darkness of their own background rendered them practically invisible.

But no one in the spy boat was looking behind him. All were straining
their eyes for the man they had come to meet. Excepting for the gentle
voices of the night there was not a sound. Then a whistle rose from
the spy boat--a short, sharp note thrice repeated. From the darkness
an answer sounded a dozen rods distant. Then footsteps were heard, as
some one picked his way uncertainly along the sloping bank. Suddenly
the footsteps ceased and stillness reigned. Roy instantly comprehended
the fact that the person approaching had paused to listen. His heart
gave a leap of joy. He himself had heard no alarming noises, but he
instantly guessed that something had caught the ear of the stranger.
And Roy knew that his companions who had come by motor-car must have
made these sounds. Trembling with excitement, he gripped Henry's
shoulder.

On came the man. Now the scouts could vaguely distinguish his form.
He called in a low voice, and some one in the spy boat answered.
Suddenly the man turned sharp about. From the darkness behind him came
the unmistakable sound of a pebble kicked by a human foot. In the
opposite direction a stone rolled down the bank and splashed noisily
into the water. With an oath, the man on the bank turned and ran
toward the motor-boat. To right and left in the darkness came the
scurrying of feet and the command "Halt!" The fugitive leaped forward.
Frantical