o you Mr. Hall, that there was a timing
device? It seems plausible to you that men who are engaged in such
desperate business would leave such a thing to the mere chance of
finding their victim home at the time their device was set to go
off?"

"Well, perhaps not, Professor, but what else is there?"

"Nothing, yet, Mr. Hall, but let us look about."

Professor Brierly, with Jimmy and Matthews close at his heels,
went picking his way through the wreckage. He stepped outside and
looked carefully among the debris. The force of the explosion
seemed to have propelled a major portion of the wreckage in the
direction of the backyard. It was here that Professor Brierly
found a section of a papered wall with a telephone bell-box
attached.

He looked long and earnestly at a spot of the paper near what had
been the bottom of the box. With Matthews' help, he forced open
the enameled lid, exposing the wires, binding posts, terminals and
bell. From among the wires he carefully picked out a frayed piece
of gray thread. He once more peered intently into the box and at
the papered area of wall to which it was attached.

"John," he said, holding the thread up for the young man's
inspection. "Does this properly belong to a telephone box of this
type?"

Matthews looked curiously at the bit of frayed thread. He shook
his head. "I can't understand what it's doing there, Professor."

"And yet, John, this bit of thread had a very definite function, a
very definite and murderous function, indeed. I think I am
beginning to understand. Now let us go look for a timing device."

"But you said there wasn't any timing device, Professor,"
protested Jimmy. "At any rate," answering the old man's glare,
"that it appeared illogical that a timing device was employed."

"Nevertheless, Mr. Hale, there was a timing device, not the kind
Mr. Hall had in mind, perhaps, but some timing device. The
explosion you will admit was timed very accurately indeed."

He walked outside, followed by his two companions. He walked
briskly toward the patch of woods. Here he entered a faint path
that was evidently used by those who came to this street from the
state road. He walked carefully along the edge of the woods
skirting the road on which was the wrecked house. A few yards from
the path he came to a cleared patch.

He stopped and looked about him. He pointed to the ground. He
said:

"Trailing is one of the accomplishments that was unfortunately
left out o