s. "The box has been opened by
mistake. They're coming out! Run, everybody!"

Turning, he caught hold of Bob, who was nearest him, and began pulling
him along.

The flight of the professor was contagious. Every one near turned and
fled, and Jerry, looking over his shoulder, saw what seemed to be a
black cloud of smoke coming from the black box.

The heart of the tall, young soldier seemed to fail him. After all,
had a mistake been made? Was it possible that a spy was using the
innocent and sometimes absent-minded professor for some base and
terrible end? Could there have been a substitution made, and one of
the harmless boxes of the scientist exchanged for a deadly bomb which
he had, unwittingly, introduced at headquarters, so that, exploding,
it might kill a number of valuable officers?

These thoughts flashed through Jerry's mind as he ran along beside
Ned. The black cloud from the box was becoming more dense.

"Maybe it's only a smoke bomb," thought Jerry. "Or perhaps the powder,
or whatever is in it, has become wet, because of so much rain, and is
only burning instead of exploding. I hope so."

Then came a yell from some one. It was followed by several other cries
of physical distress.

"Maybe it's a new kind of poison gas the Germans have taken this means
to set off," mused Jerry as he leaped along. "But I don't smell
anything. Could it be possible that spies have played this trick on
the professor?"

Jerry well knew that even with all his absent-mindedness and his blind
devotion to science, that Professor Snodgrass would never, willingly,
do anything to harm the Allied cause.

And yet----

More yells came from the soldiers that had been gathered around the
black box and who fled when Professor Snodgrass gave the alarm. And
the yells began to come from some of the officers, too. They were not
above giving vent to either pain or surprise.

And then suddenly Jerry felt a sharp pain on the back of his neck. At
first he thought it might have come from some missile, discharged
noiselessly from the black box. He clapped his hand to the seat of the
pain and at once became aware that he had struck and crushed some
small insect. It came away in his hand, twisting and curling in its
death agony, and the pain in Jerry's neck increased.

"Why!" he cried as he saw the bug. "Why, it's a wasp! A wasp!"

"Of course it is!" said Professor Snodgrass, flapping his arms about
his head, and Jerry now saw the reason. A