a question now and
then. Mind if I smoke?"

"Go right ahead," said Garvers, fumbling out a lighter. "Just don't
spill ashes on the rug.

"This all began on the Third of May. I was working here on some
top-security stuff. I had suddenly got the feeling of being watched. I
know it seems silly, what with all the check points that a potential spy
would have to go through to get here, but that's just how I felt.

"Several times I glanced around the office, but of course it was empty.
Then I began to think that it was my nerves."

"You always were a bit of a hypochondriac," observed his friend.

"Be that as it may," continued Garvers, "it was the only explanation I
had at the time. Either someone was watching me, which seemed
impossible, or I was beginning to crack under the strain.

"Well, I put my papers away and tried to take a short break. I was
reaching into my drawer where I keep magazines when, so help me, a man
stepped out of the wall into my office."

"What? It seems as if you just said a guy stepped out of the wall."

"That's just what I did say. It sounds crazy, but let me finish, will
you? I'm not kidding, and I'll show you proof later if necessary.

"Anyway, this bird stepped straight out of the wall as if it had been a
waterfall or something, but the wall itself was undamaged. The only
proof I had that he had actually done it was the fact that he was in my
office, but that was proof enough.

"To put it mildly, I was thunderstruck. After jumping to my feet, I
could only stand there like an idiot. I was so shaken that I couldn't
speak a word. But he spoke first.

"'General Garvers?' he asked, just as if he had run into me at a
cocktail party or on the street.

"I told him he was correct, and asked him who _he_ was and what he
wanted. And how he got into my office.

"He identified himself as a Henry Busch and explained that he was acting
in behalf of a good friend of his, the late Dr. Hymann Duvall. Have you
ever heard of Duvall, Max?"

His friend twisted his face in thought. "Can't say that I have,
off-hand. But the name seems to ring a bell somewhere."

"Well, anyway, he said that Duvall had perfected an invention of great
national importance shortly before his death and asked Busch to deliver
it to the government if anything should happen to him. Then Duvall died
suddenly of a heart attack."

"And what was this invention?"

"Isn't it obvious? A machine that would enable a man to walk throug