But the weird seal had started wild, imaginative tales of terror. And ugly, mob-inspiring rumors were persisting.
"I was out on that emergency Tennessee broadcast for two hellish weeks," Lundbalm growled dourly. "It was a ghastly experience. I'll never get over it."
"Well, it can't happen here!" Lieutenant Howard guaranteed flatly. "You tend to your gadgets. I've got us all locked in this room. Leave the protection to me."
Lundbalm reached for a phone. "I'll check again with Lewis over in the main announcer's cage at the dam." He started to plug into one of a row of connections.
His hand never finished the movement.
Behind him, from a silently opening trap in the ceiling, a yellowish egg-shaped object dropped to the floor, cracked open with a quick hissing sound. Instantly, an acrid, faintly greenish gas curled swiftly upwards, filling the long room with paralyzing, blistering fumes.
Lundbalm staggered back from the instrument table, his hands clutching his throat. He stumbled against Lieutenant Howard who was blindly trying to fire his heavy service Colt up at the hideously masked face leering down at them through the opened ceiling trap.
A black-sleeved arm laced across the opening, and a knife flashed downward through the curling, greenish vapor.
The raised Colt clattered to the floor from Lieutenant Howard's fingers as the steel blade plunged hilt deep through his neck. He fell, twisting in death, his clawing hands dragging Lundbalm's gas-strangled body down with him.
Blood spurted from his throat, spilling redly over the chief engineer's beefy back as the other radio control men and the three heavily armed soldiers collapsed and fell where they stood.
Not a strangled cry had broken the swift, silent action, so rapidly had the deadly gas choked out their lives.
A black-robed, hooded figure dropped quickly through the trap and stood reaching up, his face hidden within the startlingly weird gas mask covering his head.
"Hand it down!" he ordered in a terse, gratingly harsh voice.
The black-robed arm of a similarly hooded and masked figure reached through the hole in the ceiling, passed a round, flat leather-covered parcel into those extended hands. Then the second man swung down through the opening, dropped to the floor.
With scarcely a glance at the ten dead engineers and soldiers sprawled in grotesquely pitiful huddles about the room, the two robed figures crossed wordlessly to the control switchboard. Working with expert speed, one of them disconnected several wires while the other opened the flat leather case, removed from it a black wax radio recording disc.
The first man turned abruptly, strode directly to a far corner of the long room, and came back carrying a standard studio electric portable phonograph. He hooked it up to the broadcast wires he had unfastened, glanced briefly at the wall clock, and put the black wax record on the machine.
"Good timing," his rasping voice commented. "One minute to twelve!"
His fingers flicked beneath his robe, came out holding a single small grey seal. Its design was an hour-glass, and a blood-red capital "I" was drawn upright through the stem.
He stepped quickly over to the body of Lieutenant Howard, moistened the back of the strange emblem with the army officer's blood, stuck the mysterious seal on the dead man's forehead.
His movements were swift, nerveless, as devoid of emotion as though he'd merely hurriedly pasted a stamp on a letter. He stepped back to the instrument desk, started the phonograph disc revolving, and poised the sensitive reproducing needle above the fine outer lines at the edge of the record.
"The President's uninvited ghost goes on the air in exactly thirty-five seconds," he said with low-voiced, exultant grimness.
The second robed figure, standing ready with one hand on a master-control switch, asked in a flat, dried voice:
"You sure we can get out of here all right?"
"Yellow?" Sneering contempt grated in the first man's quick, snarling retort. "The Imperator's experts never miss! We'll walk out, you fool, like ministering monks in the confusion when the dam blows!"
Slowly, nervelessly, the needle lowered toward the ominously whirling black record—A half mile away, at Rock Canyon Dam, the sweltering crowds shuffled restlessly in the hot noonday sun that beat down upon the colorful pageantry.
Enormous American flags draped the sheer walls of the gigantic dam, ready to be raised majestically on gaily bannered wires when the sluices opened at the President's pressure on an electric control key. The President himself, with his chosen administration officials and vigilant Secret-Service guards occupied a temporary, flag-draped stand in a niche cut into the rock wall above the dam.
From the horns of the public address system the National Anthem, played by the Marine Band in the nation's capital, swayed the eager watchers crowding the canyon's rugged, railed rim, and poured inspiringly from the radios of millions of listeners.
The Arlington-timed clock in the main announcer's cage at the near end of the dam showed ten seconds to noon. Mort Lewis, the veteran radio announcer, nodded to Toby, his assistant, and leaned tensely close to his microphone.
As the final rousing strains of the Marine Band faded, Lewis' clear baritone voice came over the air and through the canyon speakers along the rocky walls:
"And now, ladies and gentlemen of America, the nation's Chief Executive is about to speak from Rock Canyon Dam—the President of the United States!"
A pause. Then the President's kindly, sincerely convincing voice: "My friends—"
Without warning, the President's voice was cut off by a sharp, amplified click.
For a bare fraction of a second there was a scratching sound, followed instantly by a swift, brassy, metallic flow of startling words:
"This is the Imperator of the Two Americas speaking for the citizens of the rising Invisible Empire! Rock Canyon Dam, a futile project of a weak, incipient government, will be destroyed by explosives in exactly one hundred seconds. Future public disasters will follow until the purpose of constructive anarchy has been attained. Sixty seconds now remain before the explosion. I, the Imperator, have spoken!"
The chilling, metallic voice stopped with a clipped snap that was like a hammer blow on glass.
For a terrifying, suspended moment dead silence fell upon the air and gripped the assembled officials and spectators at Rock Canyon in a paralysis of helpless dread. Then pandemonium broke loose.
The crowds surged back away from the canyon's railed rim—fighting, shouting, cursing. Army officers, soldiers and state police rallied vainly to direct a swift, safe escape for the hysteria-crazed mauling mob.
Women and children were trampled underfoot. Strong men were knocked down by the wild, blundering rush. Screams drowned out the frantically shouted commands of the officers.
Three Secret Service guards grabbed the President bodily, rushed him back off the platform, hurried him out into a cleared roadway where they, with the willing help of his official party, made a white-faced, desperately protecting ring with their bodies.
Down on the rim of the dam, Mort Lewis shouted futilely into his dead
