On they went. Not yet had they come in sight of the fugitive craft in front of them. The pilot increased his speed, leaning anxiously forward as he peered through the darkness. Over the sides of the boat his fellows craned their necks, searching the blackness for a glimpse of the quarry.
Suddenly they became aware that the motor ahead of them had stopped. Then masses of shadow seemed to close in on either hand, making the water itself darker than ever. The boat ahead had turned off its power and was propelled only by the momentum it had gained. Instinctively Roy laid his hand on the pilot's shoulder. But the latter had already stopped his 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. Frantically the men in the spy craft were trying to head their boat about. The fugitive reached it and leaped aboard. Then he turned to face the figures rushing toward him. At the same instant the scout boat suddenly moved forward. From the spy boat a pistol-shot rang out. Before another could follow, an electric torch was shining full on the spy craft, and the agent in the scout boat was covering the fugitives with his automatic.
"Drop that gun!" he commanded. "Hands up, or I'll fire!"
Taken by surprise, the man who had just boarded the craft let his weapon clatter to the floor. And in the sudden illumination Henry saw with exultation that the man was the motor-car driver, the German agent, Sanders.
"Hands up!" repeated the secret service man imperatively, noticing that one of the fugitives was crouching in the bottom of the boat with his hands hidden. In reply the man straightened up. Like a flash his arm shot out and a pistol cracked. But before a second bullet could follow, a form leaped into the shallow water and a great fist shot into the man's stomach, doubling him up like a jack-knife. The same hand then grasped the nose of the spy craft and dragged it toward the shore, while the pilot of the scout boat brought his craft close beside that of the spies. Other torches flashed in the darkness, and one by one the fugitives were manacled—Sanders, and the spy from the cliff, and the German grocer, and his errand boy, and a stranger who ran the boat.