"Oh, all right," fretted Henry. "I'll get rid of them."

Dinner was a thing of the past, and Major Coggleston, Professor Paulsen and Henry were settled comfortably on the front porch, enjoying the quiet of the summer evening.

"If these gla.s.ses of yours work as well as you say they do, the Army certainly can use them," commented the major thoughtfully. "Such an invention would completely revolutionize espionage and its counter-measures. Nothing would be safe! Why, a spy could stand half-a-mile from the laboratory I'm supposed to be protecting, look through the walls to the records room, and steal the formulae for our latest explosives right from under our noses, with none of us the wiser."

"Yes." The professor nodded. "I can see how much it would mean. That's why I had you over tonight--wanted you to have a chance to investigate."

A pause. "By the way, how's the work coming at the laboratory?"

"Better than we'd hoped for, Joe. We've got a young fellow in charge who's a genius on explosives." The major hesitated for a moment, then continued: "Confidentially, I understand he's just developed a new powder that makes TNT look like something to use for loading firecrackers. It's the greatest thing in years. The n.a.z.is and j.a.ps would give their eye-teeth for it. It's simpler to make than gunpowder, even--"

_Brrrnng!_

"I'll answer," said Henry. He skittered inside to the telephone.

A minute later he was back.

"It's for you, Major Coggleston."

The officer hurried to answer. When he returned, his face was tense with worry.

"Something's wrong!" he rapped. "It looks like the n.a.z.is have made a play for that formula already! I've got to get right back to the laboratory!"

Henry and the professor still were excitedly discussing this news when, half an hour later, the 'phone rang again. This time the tall scientist answered. He returned to the porch frowning.

"That was Coggleston," he reported. "Apparently the spy didn't get the formula, but he made a clean getaway, and he killed a sentry to do it."

"Oh, that's terrible!" Henry was afire with indignation. "Of all things!

Killing a sentry--"

"Yes." The professor nodded. "The trouble is, Coggleston says they don't have much to go on. No description, except that he was big and had red hair--"

"Red hair!"

"Yes. Red hair." The savant eyed Henry suspiciously. "Why does that surprise you so?"

"Why ... er ... oh, it doesn't. I mean--"

"What do you mean?"

"Really, Joseph, it's nothing." The little man squirmed nervously, his goatee hanging guiltily to one side. "I'm not surprised at all. Really I'm not!"

"Oh, you're not, aren't you?" Professor Paulsen started across the room with grim 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 gla.s.ses had red hair--"

"The man who bought your X-ray gla.s.ses!"

"Joseph! You're hurting!"

"What do you mean, 'the man who bought your X-ray gla.s.ses'?" 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 gla.s.ses, 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 gla.s.ses?" 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--"