the man who called himself
Simpson.

"Guess he got away," said Tom, when he and Ned had circled about and
investigated many clumps of bushes, trees, stumps and other barriers
that might conceal the fugitive.

"I guess so," agreed Ned. "Unless he's hiding in what we might call a
shell crater."

"Hardly that," and Tom smiled. "Though if all goes well the men who
operate this tank later may be searching for men in real shell holes."

"Is this one going to the other side?" asked Ned, as the two walked
back toward the tank.

"I hope it will be the first of my new machines on the Western front,"
Tom answered. "But I've still got to perfect it in some details and
then take it apart. After that, if it comes up to expectations, we'll
begin making them in quantities."

"Did you get him?" asked Mr. Damon eagerly, as the two young men came
back to join Mary and her friends.

"No, he got away," Tom answered.

"Did he try to blow up the tank?" asked Mr. Nestor, who had an abnormal
fear of explosives. "Was he a German spy?"

"I think he's that, all right," said Ned grimly. "As to his endeavoring
to blow up Tom's tank, I believe him capable of it, though he didn't
try it to-night--unless he's planted a time bomb somewhere about, Tom."

"Hardly, I guess," answered the young inventor. "He didn't have a
chance to do that. Anyhow we won't remain here long. Now, Ned, what
about this chap? Is he really the one you saw up in the tree?"

"I not only saw him but I felt him," answered Ned, with a rueful look
at his fingers. "He stepped right on me. And when he came inside the
tank to-night I knew him at once. I guess he was as surprised to see me
as I was to see him."

"But what was his object?" asked Mr. Nestor.

"He must have some connection with my old enemy, Blakeson," answered
Tom, "and we know he's mixed up with Schwen. From the looks of him I
should say that this Simpson, as he calls himself, is the directing
head of the whole business. He looks to be the moneyed man, and the
brains of the plotters. Blakeson is smart, in a mechanical way, and
Schwen is one of the best machinists I've ever employed. But this
Simpson strikes me as being the slick one of the trio."

"But what made him come here, and what did he want?" asked Mary. "Dear
me! it's like one of those moving picture plots, only I never saw one
with a tank in it before--I mean a tank like yours, Tom."

"Yes, it is a bit like moving picture--especially chasing S