glistened with all the colors in the spectrum; while under the filmed bulges of glass his eyes looked as large as apples. The Secretary felt a chill of superstitious fear as he gazed at that weird and glittering figure with its enormous glazed eyes.

"But you aren't invisible," he said at length.

"That comes now," said Thorn, walking ahead of the Secretary while on the ceiling above him danced red and yellow and blue rainbows of refracted light.

He stepped onto a big metal plate. Suspended above was a huge metal ring, with its hole directly over the spot on which he stood.

"Soft magnets," explained Thorn. "As simply as I can put it, my process for rendering an object invisible is this: I place the object, coated with the film, on this plate. Then I start in motion the overhead ring, creating an immensely powerful, rapidly rotating magnetic field. The rotating field rearranges the atoms of this peculiarly susceptible film of mine so that they will transmit light rays with the least possible resistance. It combs the atoms into straight lines, you might say. With that straight-line, least-resistance arrangement comes invisibility."

"I don't quite see—" began the Secretary.

"Refraction of light," said Thorn hurriedly. "The light rays strike this film, hurtle around the object, it coats—at increased speed, probably, but there are no instruments accurate enough to check that—and emerge on the other side. Thus, you can look at a body so filmed, and not see it: your gaze travels around it and rests on objects in a straight line behind it. But you'll see for yourself in a moment. Pull that switch, there, will you? And leave it on for two full minutes after you have ceased to see me."

Straight and tall, a figure encased in shimmering crystal, the scientist stood on the metal plate. Hesitant, with the superstitious dread growing in his heart, the Secretary stood with his hand on the switch. That hand pulled the switch down....

Soundlessly the overhead metal ring began to whirl, gathering speed with every second. And then, though he had known in advance something of what was coming, the Secretary could not suppress a shout of surprise.

The man before him on the metal plate was vanishing.

Slowly he disappeared from view—slowly, as an object sinking deeper and deeper into clear water disappears. Now the face was but a white blob. Now the entire body was but a misty blur. And now a shade, a wavering shadow, alone marked Winter's presence.

The Secretary could not have told the exact instant when that last faint blur oozed from sight. He only knew that at one second he was gazing at it—and at the next second his eyes rested on a rack of test-tubes on the wall beyond the plate.

He looked at his watch. Sweat glistened in tiny points on the hand that held the switch. It was all so like death, this disappearance—as if he had thrown the switch that electrocuted a man.

The specified two minutes passed. He cut off the power. The great ring lost speed, stopped whirling. And on the plate was—nothing.

At least it seemed there was nothing. But a moment later a deep voice sounded out: "I guess I'm invisible, all right, according to the expression on your face."

"You are," said the Secretary, mopping his forehead, "except when you speak. Then I have the bizarre experience of seeing glimpses of teeth, tongue and throat hanging in mid-air. I'd never have believed it if I hadn't witnessed it myself! That paint of yours is miraculous!"

"A little complicated, but hardly miraculous. It has a cellulose base, and there is in it a small per cent of powdered crystal—but the rest I'll keep locked in my brain alone till my country has need of it."

The glimpses of teeth and tongue and throat ceased. In spite of himself, the Secretary started as an unseen hand touched his shoulder.

"Now,"—there was ringing resolution in the deep voice—"for the Arvanian Embassy. Please drive me there—and be as quick as you can about it. I can't last very long with this film sealing most of the pores of my body."

The Secretary started for the laboratory door. Beside him sounded the patter of bare feet. He opened the door and walked into the hallway. Behind him, apparently of itself, the door clicked shut; and the footsteps again sounded beside him.

The Secretary walked to the curb where his limousine waited. His chauffeur jumped out and opened the door. The Secretary paused a moment, one foot on the running board, to draw a cigar from his pocket and light it. During that moment the car pressed down on that side, and as suddenly rocked back up again.

The chauffeur stared wide-eyed at his employer.

"Did you do that, sir?" he asked.

"Do what?" said the Secretary.

"Push down on the running board with your foot."

"Of course not," said the Secretary, his eyebrows raising. "You could have seen my leg move if I had. But why do you ask?"

"It felt like somebody got into this car," mumbled the man.

"Did you see anybody get in?" said the Secretary with a shrug. And, shaking his head, with a fuddled look in his eyes, the chauffeur turned away and got into the driver's seat.

The Secretary glanced at the rear seat. On the far side, the cushion was heavily depressed. He sat on the near side, feeling his knee strike another, unseen knee.

"Drive to the Bulgarian Embassy," he told his man.

Up Sixteenth Street the car swung, past the various embassies which looked more like palatial private villas than offices of foreign nations. Toward the end of the line, a smaller building than most of the others, was the Arvanian Embassy. Next to it was the Bulgarian.

The car stopped in front of the Bulgarian Embassy, and the Secretary got out. Again he paused, while the chauffeur held the door open, to hold a match to his cigar. Again the car sagged down on that side, and slowly swayed up again.

"Hey—" said the chauffeur. But meeting the Secretary's calmly inquiring gaze, he stopped. Scratching his head, he went back to the wheel, while the Secretary walked toward the building entrance.

Behind him, moving on soundless bare feet along the sidewalk, Thorn Winter hastened, cloaked in invisibility, toward the Arvanian Embassy—and the plans that spelled America's destruction if they remained in Arvanian hands.

The embassy building was a three-storied oblong house of white stone topping a terrace that started its climb from the sidewalk of Sixteenth Street. The doors at the head of the wide stone staircase were of bronze; and they were closed, and, Thorn surmised, efficiently barred. The windows at front and sides were also closed, in spite of the warmth of the sunny spring afternoon.

Beside the building, leading up in a short steep hill, was the driveway. Up this Thorn started. The front of the house was hopelessly barred; but at the rear entrance there might be a chance.

Up the driveway, then, he walked, a little startled at the fact that he cast no shadow—feeling as a ghost might feel. The pavement was hot to his thinly filmed feet. A little dubious as to the effect of heat on the vital shell that hid him, he stepped off into the cool grass beside the drive; and came soon to the rear of the embassy.

There was no porch or veranda, simply two stone steps leading up to a stout oak door which opened onto the embassy kitchens. From behind this door came the sound of crockery and the hum of voices. The Arvanian chef evidently was preparing afternoon tea.

Walking boldly to the very steps, Thorn began the vigil that should end when someone came in or out of that door, allowing him to slip inside the building before the portal was barred shut again.

For nearly half an hour Thorn stood there before something happened that at once helped him, and, at the same time, nearly proved his undoing.

A light delivery van sped up the driveway. The wheels stirred