Will declared.

The cutting had been done between the second level and the top. The
ladders below seemed perfectly safe. After testing them thoroughly, Will
trusted himself on one of the rungs and let himself down slowly, bearing
as much weight as was possible on the standards.

He was at the bottom in a moment, and in another moment stood by the
side of his chums with the saw in his hand.

"I don't think that's so very much!" Tommy exclaimed.

"Right here, then," Will explained, "is where you get your little
Sherlock Holmes lesson! This is a new saw, as you all see. It probably
never was used before. Now the man who did the cutting bought this at
some nearby store. Don't you see what it means?"

"That's a fact!" cried Tommy. "We can find out who bought the saw, and
so discover the gink who tried to commit murder by sawing the ladders."

"And look here," Will went on, "do you see these threads hanging to the
teeth of the saw? Do you see the color?"

"Blue!" replied the boys in a breath.

"That's right, blue. Now, what sort of a suit did the detective wear
this morning? It was blue, wasn't it?"

"Sure it was!" replied George. "A blue serge! I noticed it particularly
because it wasn't much of a fit."

"Well, these are blue serge threads!" commented Will.

"That's right, too," admitted Sandy.

While the boys still stood at the second level they heard some one
moving down from the top. Will rushed around to the ladder and looked
up.

He could not see the face of the man who was climbing down, but he could
see that he did not wear a blue serge suit.

In a moment he called out to him, asking some trivial question regarding
the action of the pumps. When the man looked down he saw that it was
Canfield. The caretaker seemed surprised at finding the boys at the
second level. He kept on descending.

"Wait!" Will called. "Stop where you are!"

"But I've got to find out what's the matter with the machinery at the
bottom," the caretaker called out. "There's something wrong there!"

"Then you'd better take long steps," replied Will, "for if you put any
weight on those rungs, you're likely to land at the bottom of the shaft.
The rungs have been cut!"

"I can't believe that!" replied Canfield.

"Suppose you look and see!"

The caretaker advanced cautiously downward until he came to where a fine
line of sawdust lay on one of the rungs.

"Do you know who did this?" he asked.

"We think we do," replied Will, "bu