crazy man you were in
touch with six months ago, who prophesied this! We turned him down! He
showed me a watch and said the salvation of the world was inside the
case! I thought him insane!"

* * * * *

"You mean Luke Evans, sir. That watch was his pocket model. He went
off in a huff, saying the time would come when we'd want him and not
be able to find him."

"But, damn him, he wanted to produce universal darkness, or some such
nonsense, Rennell, and I told him that we wanted light, not darkness."

"It wasn't exactly that, sir." Colonel Stopford was a man of the old
school: he had been an artillery officer in the Great War, and was
characteristically impatient of new notions. Dick began carefully:
"You'll remember, sir, old Evans claimed to have been the inventor of
that shadow-breaking device that was stolen from him and sold in
England."

"To a moving picture company!" snorted Stopford. "I asked him what
moving pictures had to do with war."

"Evans was convinced that the invention would be applied to war. He
claimed that it made the modern methods of military camouflage out of
date completely. He said that by destroying shadows one could produce
invisibility, since visibility consists in the refraction of wave
lengths by material objects.

"When they stole his invention, he foresaw that it would be used in
war. He set to work to nullify his own invention. He told me that he
had unintentionally given to the enemies of the United States a means
of bringing us to our knees, since he believed that British motion
picture company was actually a subsidiary of Krupp's. He worked out a
method of counteracting it."

"You must get him, Rennell. Even if it's all nonsense, we can't afford
to let any chance go. If Evans's invention will counteract this damned
invisibility business--"

The telephone on the Colonel's desk rang. He picked it up, and his
face assumed an expression of incredulity. He looked about him, like a
man bewildered. He beckoned to the police official, who hurried to his
side, and thrust the receiver into his hand. The official listened.

"All right," he said. He turned to Dick and the Civil Service
representative.

"Gentlemen," he said, "the President has disappeared from his office
in the White House, and there are grave fears that he has been
kidnapped!"

CHAPTER III

_In the White House_

Colonel Stopford's car had been parked around the corner of the
bu