.

In mid-morning another pushpot fell screaming from the skies. That made
six pushpots and six pilots for this week--two today. The things had no
wings. They had no gliding angle. Pointed up, they could climb
unbelievably. While their engines functioned, they could be controlled
after a fashion. But they were not aircraft in any ordinary meaning of
the word. They were engines with fuel tanks and controls in their
exhaust blast. When their engines failed, they were so much junk falling
out of the sky.

Joe happened to see the second crash, and he didn't go to noon mess at
all. He hadn't any appetite. Instead, he gloomily let himself be packed
full of irrelevant information by the young lieutenant who considered
that since Joe had been sent by security to look into sabotage, he must
be given every possible opportunity to evaluate--that would be the word
the young lieutenant would use--the situation.

But all the time that Joe followed him about, his mind fumbled with a
hunch. The idea was that there was a pattern of thinking in sabotage,
and if you could solve it, you could outguess the saboteur. But the
trouble was to figure out the similarity he felt existed in--say--a
private plane shooting rockets and overhaul mechanics planting booby
traps and faked shippers getting bombs on planes--and come to think of
it, there was Braun....

Braun was the key! Braun had been an honest man, with an honest loyalty
to the United States which had given him refuge. But he had been
blackmailed into accepting a container of atomic death to be released in
the Shed. Radioactive cobalt did not belong in the Shed. That was the
key to the pattern of sabotage. Braun was not to use any natural thing
that belonged in the Shed. He was to be only the means by which
something extraneous and deadly was to have been introduced.

That was it! Somebody was devising ingenious ways to get well-known
destructive devices into places where they did not belong, but where
they would be effective. Rockets. Bombs. Even radioactive cobalt dust.
All were perfectly well-known means of destruction. The minds that
planned those tricks said, in effect: "These things will destroy. How
can we get them to where they will destroy something?" It was a strict
pattern.

But the pushpot sabotage--and Joe was sure it was nothing else--was not
that sort of thing. Making motors explode.... Motors don't explode. One
couldn't put bombs in them. There wasn't room. The expl