He couldn't hear you," whispered George. "You'll have to make more
noise than that."

Again Grant rapped upon the glass, pounding on the window sash also in
his efforts to arouse the attention of the man within.

All four boys now were keenly excited and all were eager to discover
what the intruder would do, now that his presence had been discovered.

To their surprise the man did not respond to the summons. Even his
position was unchanged and in the dim light the boys were unable to
decide whether or not he had even glanced in the direction from which
the hail had come.

"There's only one thing we can do," said George.

"What's that?" demanded Grant.

"Go around to the other side and tell Fred we've got to have the door
unlocked. Then we'll make a rush on the fellow before he knows that we
are after him."

The suggestion was quickly followed and soon the four boys were
standing together in front of the side-door which opened upon the dock.

"Now, then," said Fred, who insisted upon retaining his key, "when I
unlock the door all four of us must make a rush together."

"That's right," whispered George as he grasped more tightly the bat
which he was holding in his hand.

"Let String and George go ahead. They are the best armed," said Grant.

For some reason Grant was less excited than his companions, a fact
which escaped the attention of the boys at that time.

"All ready!" whispered Fred. Quickly turning the key he opened the door
and together the four boys darted into the boat-house.

Although the moon was shining, the interior of the room was somewhat
darker than it had been on the dock. The boys, however, were able to
see clearly the man who was still standing near the Black Growler. Not
even when they rushed upon him did he turn his face toward them.

In their eagerness to secure him all four did their utmost to leap upon
him at the same time.

A most amazing result, however, followed their desperate attempt.
Despite his efforts to save himself, Fred, who pluckily was in advance,
was pushed over the edge of the slip and with a loud splash fell into
the river. Before he could check himself John followed his example. A
yell came from Fred when he arose to the surface because at that moment
the intruder, whom they had discovered in the boat-house, also followed
the example set by the boys.

Meanwhile George and Grant had broken into loud laughter. George was
bowed and slapping his sides as he moved ab