Up the stairs he made his way until he came to an empty loft. Quickly he went over to the blank wall and began feeling cautiously about as if for a secret spring hidden in the plaster.

"No one in the back room," said Kennedy rejoining me in the den itself with the prisoner. "He's out, all right."

Before Craig was a mirror. As he looked into it, at an angle, he could see a part of the decorations of the wall behind him actually open out.

For an instant the evil face of Wu Fang appeared.

Without a word, Craig walked into the back room. As he did so, Wu Fang, knife in hand, stealthily opened the sliding panel its full length and noiselessly entered the room behind me. With knife upraised for instant action he moved closer and closer to me. He had almost reached me and paused to gloat as he poised the knife ready to strike, when I heard a shout from Kennedy, and a scuffle.

Craig had leaped out from behind a screen near the doorway to the back room where he had hidden to lure Wu on. With a powerful grasp, he twisted the knife from Wu's hand and it fell with a clatter on the floor. I was at Wu myself an instant later. He was a powerful fighter, but we managed to snap the handcuffs on him finally, also.

"Walter," panted Kennedy straightening himself out after the fracas, "I'll stay here with the prisoners. Go get the police."

I hurried out and rushed down the street seeking an officer.

Up in the den, Wu Fang, silent, stood with his back to the wall, scowling sullenly. Close beside him hung a sort of bell-cord, just out of reach. Kennedy, revolver in hand, was examining the writing-table to discover whatever evidence he could. Slowly, imperceptibly, inch by inch, Wu moved toward the bell-cord. He was reaching out with his manacled hands to seize it when Kennedy, alert, turned, saw him, and instantly shot. Wu literally crumpled up and dropped to the floor as Craig bounded over to him.

By this time I had found a policeman and he had summoned the wagon from the Elizabeth Street station, a few blocks away. As we drove up before the den, I leaped out and the police followed.

Imagine my surprise at seeing Wu stretched on the floor. Kennedy had tried to staunch the flow of blood from a wound on Wu's shoulder with a handkerchief and now was making a temporary bandage which he bound on him.

"How are you, sergeant?" nodded Kennedy. "Well, I guess you'll admit I made good this time."

The sergeant smiled, recalling a previous occasion when the slippery Wu had squirmed through our fingers.

Kennedy's restless eye fell on the bell-rope which had caused the trouble. Somehow, he seemed to have an irresistible desire to pull that rope. He gazed about the room.

"Walter, you and the sergeant take the prisoners into the next room,"

he said. "I want to see what this thing really is."

We moved Wu and his servant and stood in the doorway. Craig gave the rope a yank.

Instantly there was an explosion. A concealed shotgun in the wall fired, scattering shot all over the front of Wu's table, just where we had been standing, knocking over and breaking vases, scattering papers and in general wrecking everything before it.

"So, that's it," whistled Craig. "You fellows can come back now. Two of you men I'm going to leave here to watch the place and make other arrests if you can. Come on."

With Kennedy I left the tenement while the sergeant marched the prisoners out, and we drove off with them. Quite a crowd had collected outside by the time we came out. Among them, naturally, were many Chinamen, and we could not see two of them hiding behind the rest on the outskirts, jabbering in low tones together and making hasty plans.

As we clanged away down the street they followed more slowly on foot.

Common humanity dictated that we take Wu first of all to a hospital and get him fixed up and to a hospital we went. Kennedy and I entered with our prisoners, closely guarded by the police.

Craig handed Wu over to two young doctors and a nurse. By this time Wu was very weak from loss of blood. Still he had his iron nerve and that was carrying him through. The two young doctors and the nurse had scarcely begun to take off Craig's rude bandage to replace it properly, when a noise outside told us that a weeping and gesticulating delegation of Chinese had arrived.

"Keep 'em back," called one of the doctors to an attendant. The attendant tried to drive them away, but nothing could force them back more than an inch or two as, in broken English, they sought to find out how Wu was. Their importunity proved too much for only one attendant.

Still gibbering and gesticulating, the crowd brushed past him as if he had been a mere reed. The attendant raged about until he lost his head.

But it was no use. There was nothing for him to do but to follow them in.

Kennedy by this time had finished talking to the doctors and handing Wu over to them. They had taken him into a room in the dispensary. Just then the chattering crowd pushed in, some asking questions, others bewailing the fate of the great Wu Fang. They were so insistent that at last one of the doctors was forced to demand that the police drive them out. They started to push them back.

In the melee, one of their number managed to get away from the rest and reach the doorway to the emergency room. He was, as we found out later, dressed almost precisely like Wu, although he had on a somewhat different cap. In build and size as well as features he was a veritable Dromio.

The other Chinaman drew back behind the screen which hid the doorway to the emergency room and concealed himself.

Meanwhile, Kennedy and I were laughing at the truly ludicrous antics of the astounded Celestials, thunderstruck at the capture of the peerless leader, while the police forced them back.

"Well, good-bye," nodded Craig to the first doctor and nurse who had attended Wu Fang outside.

"Good-bye. We'll fix him up and take good care that he doesn't cheat the law," they said, with a nod to the sergeant.

In the emergency room, Wu was placed on an operating table and there was bound up properly, though he was terribly weak now.

Back of the screen, however, the other Chinaman was hiding, able to get an occasional glance at what was going on. There happened to be a table near him on which were gauze, cotton and other things. He reached over and took the gauze and quickly made it into a bandage, keeping one eye on the bandaging of Wu. Then he placed the bandage over his own shoulder and arm in the same way that he saw the doctors doing with Wu.

They had finished with Wu and one of the doctors moved over to the doorway to call the sergeant. For the moment the rest had left Wu alone, his eyes apparently half closed through weakness. Each was busy about his own especial task.

From behind the screen which was only a few feet from the operating table, the secreted Chinaman stepped out. Quickly he placed his own hat on Wu and took Wu's, then took Wu's place on the table while Wu slipped behind the screen.

The doctor turned to the supposed Wu. "Come now," he ordered, handing him over to the police. "Here he is at last."

The sergeant started to lead the prisoner out. As he did so, he looked sharply at him. He could scarcely believe his eyes. There was something wrong. All Chinaman might look alike to some people but not to him.

"That's not Wu Fang!" he exclaimed.

Instantly there was the greatest excitement. The doctors were astounded as all rushed into the emergency room again. One of them looked behind the screen. There was an open window.

"That's how he got away," he cried.

Meanwhile, several blocks from the hospital, Wu, still weak but more than ever nerved up, came out of his place of concealment, gazed up and down the street, and, seeing no one following, hurried away from the hospital as fast as his shaky legs would bear him.

Confident that at last our arch enemy was safely landed in the hands of the police, Kennedy and I had left the hospital and were hastening to Elaine with the news. We stopped at the laboratory only long enough to get the torpedo from the safe and at a toy store where Craig bought a fine little clockwork battleship.

We found Elaine and Aunt Josephine in the conservatory and quickly Kennedy related how we had captured Wu.

But, like all inventors, his pet was the torpedo and soon we were absorbed in his description of it. As he unwrapped it, Elaine drew back, timidly, from the fearful engine of destruction.

Kennedy smiled. "No, it isn't dangerous," he said rea.s.suringly. "I've removed its charge and put in a percussion cap. Let me show you, on a small scale, how it works," he added, winding up the battleship and placing it in the fountain.

Next he placed the torpedo in the water at the other end of the tank.

"Come over here," he said, indicating to us to follow him into the palms.

There he had placed the strange wireless apparatus which controlled the torpedo. He pressed a lever. We peered out through the fronds of the palms. That uncanny little cigar-shaped thing actually started to move over the surface of the water.

"Of course I could make it dive," explained Craig, "but I want you to see it work."

Around the tank it went, turned, cut a figure eight, as Kennedy manipulated the levers. Then it headed straight toward the battleship.

It struck. There was a loud report, a spurt of water. One of the skeleton masts fell over. The battleship heeled over, and slowly sank, bow first.