The common element in all those sabotage tricks was actually clear enough, but Joe wasn't used to thinking in such terms. He did know, though, that there was a pattern in those devices which did not exist in the blowing up of jet motors from inside.
He scowled and scowled, racking his brains, while the young lieutenant watched respectfully, waiting for Joe to have an inspiration. Had Joe known it, the lieutenant was deeply impressed by his attempt at concentration on the problem it had not been Major Holt's intention for Joe to consider. When Joe temporarily gave up, the young lieutenant eagerly showed him over the whole field and all its workings.
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.