"Only on the ground floor were they left locked, oh lord," answered the other. He pointed. "See! There is one second floor window open."

The aperture the Mongol indicated was the identical window through which Doc Savage had entered. And Doc now stood in the darkened room behind, listening to the talk. He understood the language — it was one of scores he could handle as fluently as he spoke English.

"No kangaroo could leap that high, much less a man!" snorted Liang-Sun Chi. "But we will search this place well. It is said that the greatest mysteries have the simplest explanations. Perhaps we left a door open this afternoon."

He produced keys, unlocked one of the doors, and waved his men in. They entered cautiously, jabbing flashlight beams ahead.

Doc retreated from the window out of which he had been watching. He passed soundlessly through a door into a corridor. At the second step, his toe was stopped by a heavy object.

A flashlight came out of his pocket. It tossed a beam that was hardly more than a white thread.

The body of a man lay on the corridor floor. A sword slash had cleaved into his heart.

THE flash ray disclosed other details about the murder victim. He was an elderly man, at least sixty. He wore plum-colored knee breeches, white stockings, a braided coat with long tails, a powdered white wig — a very flashy butler's livery.

Doc examined more closely. The flunky had been dead several hours at least.

The Orientals were making considerable noise downstairs. Draperies ripped as they were torn down. Moving furniture grated on waxed floors.

"My sons, it is a wise man who gets all his troubles in front of him," called their leader, Liang-Sun Chi. "Search the basement."

Liang-Sun seemed to be something of a philosopher.

Working w h silence and speed, floe searched the upper floors. He found this side of the castle contained only servant quarters, gymnasium, indoor swimming pool, billiard rooms, and a few guest chambers.

Back at the open window. he glanced down. One of the guards left in the court stood directly below.

Doc returned to the second-floor corridor. At one end of this he had noted a suit of armor. The metal plates of the gear were supported on an iron framework. Inside the helmet was mounted a papier-mache cast of a face. This did not differ greatly in color from Doc's tanned features.

There was no sound as Doc dislodged the armor from its pedestal. He carried it to the open window. It weighed fully a hundred pounds.

He tossed it down on the Mongol guard. The fellow was knocked cold and battered to the ground. The armor clanked loudly on the court tiles.

Men poured into the court. Yelling excitedly, they pounced on the armor. They thought Doc was inside.

None of them heard the window at the opposite end of the building lift, or saw a mighty bronze figure that flitted, silent as a great bat, across the court to the other house.

They speared swords into cracks in the armor. Chopping furiously, one half-caste got the helmet severed.

They saw they had been fooled.

"We are but dumb dogs!" Liang-Sun squawked. "We have brought shame to our ancestors! Continue the search!"

WHILE the Mongols pushed the murderous hunt a few yards away. Doc Savage scrutinized the other half of the vast mansion. He found no traces of Juan Mindoro, or Scott S. Osborn. In the library, however, he noted the floor cords had been wrenched from some of the reading lamps. Evidently these had served to bind prisoners.

Doc was now certain the Orientals had visited the castle some hours earlier. They had slain the butler. Probably they had made off with Juan Mindoro and Scott S. Osborn.

The Mongols finished with the other side of the house. They entered the room below Doc.

"It is said the lowly fly is never caught napping because he has eyes that see in all directions," Liang-Sun singsonged. "You will do well to imitate the fly, my sons. Should this bronze devil escape, some of us may lose our heads."

The flowery speech enlightened Doc on an important point. These Mongols and half-castes were serving some master — a master who wielded the power of life and death over them.

Their chief might be one of the pair who had listened in on the talk in Doc's office with the microphone-carrying pigeon, or the gist of the conversation might have been relayed to him. It was certain the talk the Mongols had overheard had brought them to Scott S. Osborn's home — for Doc had said he was coming here.

Two slant-eyed men mounted the stairs.

Doc located a light switch, clicked it. The fixtures remained dark. Doc recalled the wires torn from the reading lamps — fuses must have been blown when that was done.

The pair coming up the stairs exchanged whining whispers.

"Cold worms of fear are crawling up and down the spine of this insignificant person," one complained. "We have made many inquiries about Doc Savage, since we were so fortunate as to learn Juan Mindoro had appealed to him for help. We heard everywhere that Doc Savage was a mighty fighter. Aiee! But no one told us he was a ghost. He must be lurking in this place, yet we have heard no sound and saw no one

"Swallow thy tongue, fool!" growled the other. "Only cowards talk of fear!"

"You are wrong. Only an idiot thinks not of danger

The Orientals had reached the top of the stairs. Now, without another word, one slowly lowered to his hands and knees. A moment later, he slouched prone on the hall carpet.

The second man eyed him foolishly. His lips writhed apart, showing teeth stained black from chewing betel nut. He seemed to be trying to cry out. Then he piled in a silent heap on the floor.

A giant, ghostly bronze figure, Doc Savage loomed over the pair. His fingers explored their clothing. He found nothing to indicate who their leader might be.

Both men snored as though asleep.

Doc retreated noiselessly down the second-floor corridor.

Liang-Sun droned words up from below. Receiving no answer from his two men, he mounted the stairs, flanked by three guardsmen and a machine gunner.

The outburst of cries as the two unconscious men were found sounded like the clamor that comes when a hawk flies into a flock of guineas.

A whispered consultation followed. Doc could not catch the words. The Orientals retreated to the lower floor, apparently to consider the situation.

"What manner of thing could have overcome our brothers?" Liang-Sun repeated over and over.

Suddenly, at the opposite end of the house, came a terrific uproar. Furniture overturned. Men gasped, cackled profanity.

"The bronze devil! He is here!" a man sang excitedly.

There was a loud clatter as the Mongols made for the noise.

Doc was puzzled. But it was too good a chance to pass up. He eased down a rear stairway, intent on quitting the place.

The stairs he chose let him into the lower floor library, a room walled with bookcases and floored with rich rugs.

The moment he stepped into it, he knew he had made a mistake. A dozen shadowy, slant-eyed men flung upon him.

THE noise at the other end of the house had been a trick to draw him down from upstairs.

The first leaping Mongol seemed to meet a bronze wall in mid-air. He was hurled back, and was impaled on the blunt sword of one who followed.

A second slant-eyed man got an open-handed slap that turned him over in the air like a Fourth-of-July pinwheel. Another found himself grasped about the chest. He shrieked, and the piercing shrillness of his voice was punctuated with the dull crack of breaking ribs.

The Mongols had not expected an easy fight. But they had not dreamed it would be like this. The giant bronze man moved with a speed that defied the eye. Sword slashes, delivered point-blank, sliced thin air. And when they did lay their hands on him, it was as if they had grasped living steel.