d the pilot. "Keep your heads below the
gunwale till they're past."

The party crouched lower. On came the spy boat. Its muffled engine
beats were hardly louder than the pounding of the hearts that watched.
It drove steadily forward. Now it was a few fathoms astern. Now it
was abreast. Now it had passed. Stealthily four heads slipped above
the gunwale of the scout boat. The spy craft was already lost in
darkness. The pilot grasped his wheel. He turned a switch and the
boat began to vibrate silently. Then it moved forward, gathering
momentum with every second. Under the covered deck the other agent
flashed a light on his watch.

"Eleven fifty-eight," he whispered. "They figured it down close."

On went the boat. The craft ahead of them was still invisible though
but a few hundred feet distant. But by peering sharply at the water,
the pilot could see where it had passed. The surface was still
agitated. Faintly came the sound of the muffled motor. The pilot
increased his speed, but no sound came from his boat. Like a ghost it
glided through the dark waters.

"Look sharp," whispered the pilot. "Let me know if you see them.
We've got to get as close to them as we can, and yet we must not be
seen."

On went the spy craft. It slid past the park. The street leading to
that was faintly illumined by occasional lights.

The pilot uttered a low exclamation of alarm. "If they look back," he
whispered, "those lights will betray us. We're right between them and
the spies."

Sharply he swung his craft to the right, crowding close to the shallow
waters that edged the channel. If he ran into the mud flats disaster
might result. But to stay where they would be silhouetted against the
street lights was to court discovery. He had chosen the lesser of two
evils.

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 h