"In a thing like this," he said presently, "you can't afford to take any chances. You've got to be dead sure; as dead sure of everything as it is humanly possible to be, from start to finish. I had utmost confidence in your making the complete flight to Natal. And the way you two did handle yourselves, when the odds were actually all against you, proves that the confidence I had in you was justified. But in everything there is ever present the little item of fate. A tiny little something that is beyond man's power to see in advance, or even to counteract when it happens. For example, that technical sergeant at Bolling Field. I would have staked my life on that man. But, as things turned out, I was completely mistaken. And so with you two, or with each of my agents at the stops you were to make. Because of something you couldn't guard against, or prevent before death came to you, the contents of one of those sealed envelopes might have fallen into enemy hands. What I mean is, one of the envelopes might have been opened, the contents read, and then the envelopes resealed."
"But, Colonel," Dawson protested, "one of us would—"
"I know, I know," the colonel said, stopping him with a gesture of his hand. "But look at it this way. Suppose von Steuben had knocked you both out while you still had the envelopes? Suppose he had opened one, read its contents, and resealed it so that you'd never have guessed? What then? When you came to and found you still had the envelopes, you'd never dream that they had been touched."
"But I'd be plenty suspicious, sir!" Dawson interrupted. "I'd—"
"Would you?" the colonel's quiet but firm voice stopped him again. "But von Steuben was no fool! What if he stole your money and Farmer's money, too? What then?"
"I see what you mean, sir," Dawson said, and grinned sheepishly. "We would have thought we'd been victims of some holdup."
"Exactly," the colonel agreed. "A crazy little twist of fate over which you had no control whatever. Yet the damage would have been done. So I had to do what I could to find out if there had been any crazy twist of fate. In other words, each of those sealed envelopes contained the information, in code of course, that the next bombing plane to pass through would carry the President, and members of his party."
Dawson blinked, and suddenly the truth hit him between the eyes.
"What, sir?" he gasped. "You—you mean this B-25 is supposed to be carrying the President?"
"I mean just that!" the colonel confirmed grimly. "If enemy agents have learned what was in those envelopes, they will believe that this bomber is carrying the President as a passenger. The President has already left Washington in secret, and it wouldn't take much checking by enemy agents to find out that he isn't at the White House. Naturally they'd believe he was aboard this plane."