“Oh!  All right, go ahead, and I’ll follow.”

A moment later Ham Spink let himself down in a little hole beside the boathouse.  Here his feet were close to the water, but he supported himself on a cross rail nailed from one section of the spiling to another.  Carl Dudder followed him, and both moved cautiously forward to the front end of the building.  Once Ham slipped and a slight splash followed.

“What’s that?” cried Carl, in alarm, for he was decidedly nervous.

“My foot slipped, that’s all,” was the answer.

“Is it deep under here?

“Not over four or five feet.”

“Where are those loose boards?”

“Right here.  Now take hold of that end and we’ll soon have them up and be inside the building,” answered Ham.

CHAPTER VIII

HOW TWO PROWLERS WERE TREATED

While Ham and Carl were moving around under the boathouse, Shep and Snap were not idle.  The doctor’s son, on awakening, had wanted to throw the flour paste out of the window at the midnight prowlers, but Snap thought of another plan.

“Come on below, and wait until they shove up the flooring,” he whispered.

The doctor’s son understood, and with caution, so as not to make any noise, the two chums came down out of the tiny loft, bringing with them the pail and the tin can of awful-smelling flour paste.

It was absolutely dark below, but they could plainly hear Ham and Carl working on the loose boards of the floor near the river end of the boathouse.  Thither they made their way, Snap with the pail and Shep with the can, both ready for action.

Slowly one board was lifted and pushed aside and a second followed.  Then two heads appeared in the gloom.

“Robbers!” cried Snap.

“Burglars!” yelled the doctor’s son.

“Shoot them!”

“Don’t let them get away alive!”

Then with a vigorous throw Snap landed his pail of stuff full upon the head of Ham Spink.  Splosh! it struck the dudish youth squarely in the face and ear.  Another splosh followed, and Carl Dudder was likewise decorated.

“Hi! wow!” spluttered Ham.  “I—–­Oh, what a smell!

“Oh, my eye!” groaned Carl.  “Phew! what’s this?”

“We’re discovered!

“What’s this they threw on us?”

“Oh, did you ever smell such stuff?”

“Robbers! thieves!” yelled Snap and Shep.  “Shoot them!  Give them a dose of buckshot!”

“They are going to shoot us!” screamed Carl Dudder, and dodged down.  Then he lost his footing on the wet and slippery rails, clutched at Ham to save himself, and both went down with a loud splash into the dirty water under the boathouse.

“There they go!” cried Shep.

“Let us scare them some more,” whispered Snap.  “Pretend you don’t recognize them.”

Quickly a lantern was lit and held over the opening in the floor.  Down below two dark forms, covered with mud and flour paste, could be seen clutching at the slippery braces of the spiling.  Snap and Shep could scarcely keep from roaring.