determination, his eyes sharp. "Well, then—"

"Joseph—"

The scientist reached for his colleague's shoulder. But the shoulder slipped away. Henry dived frantically for the doorway.

"Oh, no, you don't!"

Spinning about with surprising agility, the professor's hand speared out. It stabbed home to its goal on Henry's chin with deadly aim. Caught the little man's goatee in a grip that stopped his headlong rush dead still.

"Joseph!" screamed Henry, his eyes filling with tears. "Stop it! You're hurting!"

"And I intend to keep right on hurting until I get the truth out of you, you amoeba-brained atom!" thundered the other. "I can smell your lies a block away—and this is one time you're not going to get away with it! Now: tell me who the red-headed man was."

"I don't know, Joseph! Really—"

Professor Paulsen gave his colleague's chin-whiskers a savage jerk.

"I want the truth!" he rapped. "Hurry up! Tell me!" He jerked again.

"Oh! Ow! Joseph, please! Oh, let me go! I'll tell—"

"You bet you'll tell!" grated his friend. "It's one thing to let you get away with making a fool of me. But when it comes to tampering with the United States Army—" And then, breaking off: "All right. Why did you jump so when I mentioned the spy was believed to have red hair?"

"Well...." Henry squirmed some more. He tried hard to look dignified despite the professor's grip on his goatee, but failed miserably.

"Out with it!"

"It's really nothing, Joseph—"

"Out with it, I say!"

"Ow! Joseph, stop!" And then: "It's just ... the man who bought my X-ray glasses had red hair—"

"The man who bought your X-ray glasses!"

"Joseph! You're hurting!"

"What do you mean, 'the man who bought your X-ray glasses'?" The professor thrust his gaunt face to within an inch of Henry's, his eyes like steel gimlets. "If you tell me you've sold those glasses, you misbegotten moron—"

"But Joseph!" Henry struggled to free himself. "You told me to get rid of them. You warned me not to use them."

"I never told you to sell them! You knew I wanted to talk to Coggleston about their use to the army—"

"Yes, but you didn't tell me not to sell them. And I had all my notes, and knew just how to make another pair, and so when the red-headed man offered me fifty dollars for them—"

But Professor Paulsen had ceased to listen. Already he was on the telephone and calling Major Coggleston. Tersely he explained the situation.

Then:

"Could he have gotten the formula, Ray? Was it anywhere he could see it through those devil's glasses?" And, a moment later: "Oh. Coggleston, I can't tell you how sorry I am—"

"What did he say?" Henry demanded excitedly as the other hung up. "Is it all right, Joseph—"

"No." The scientist shook his head, eyes dark with worry. "Coggleston says we can be practically certain the spy got that formula. He says the man in charge was having a staff meeting of his aides, and they had it written out on a blackboard for discussion."

"Joseph—"

"Ray's on his way over now. He wants to ask you some questions about the man's description—"

Even as the words left the savant's mouth, they heard a car roar up the driveway. Major Ray Coggleston hurried in the door, a sergeant at his heels. He wasted no time on preliminaries.

"What did he look like?" he demanded.

"Well, he had red hair...."

"Yes, yes. We know that."

"He was pretty big. Almost as tall as Joseph."

"Yes. Go on."

"I guess he talked sort of loud."

"Got it."

Henry hesitated. Tugged at his goatee, his face screwed with concentration.

"Really, Major Coggleston, that's about all I can remember about him," he said at last.

The officer swore. He paced the floor in a frenzy of anxiety.

"We've nothing to go on!" he fumed. "The description's meaningless. It could fit any one of a thousand men in