Tom reached up swiftly and pushed over the lever that locked the two window sashes. In doing this he set his own patent burglar alarm. If that lever was turned back again, or broken, the buzzers would be set ringing all over the house, and in Koku's room over the garage.

He did not believe that the marauder on the roof of the porch could have seen the flash of his shirt-sleeved arm. But he took no chance of being observed from outside by rising to his feet.

On his hands and knees he crept away from the window, and out of the bathroom. Once there, he stood up, grabbed the portfolio, and without coat or vest and as he was, dashed out of the bedroom. He had been positive that nobody but himself was astir in the big house, and he was right.

He did not punch the light button when he entered the library. He knew where to put his hand upon an electric torch in the table drawer, and he gained possession of this.

Then he went to the safe and twirled the knob and watched the indicator find the four numbers which were the "open sesame" to the burglar and fire-proof door.

He flung the portfolio into the inner compartment, closed both doors, and twirled the combination-knob. Then Tom tiptoed to the foot of the front stairs to listen. He could hear no sound from above.

He did not want his father to be startled, if the enemy did break in; and he knew that old Rad, awakened out of a sound sleep, would be worse than useless at such a time.

After all, the giant, Koku, was his main dependence under these circumstances. Tom crept to the outer door, opened it carefully, and slipped out, letting the spring lock click behind him. For the first time he realized that he was in his shirt and trousers and wore only felt slippers on his feet.

But he was locked out now. He had no key. He must run the risk of the fine rain and the chill of the night air.

He stepped. off the end of the porch and ran around the house. It was to the roof of the rear porch that the marauder had climbed. But peer as he might from down in the yard, Tom could see no moving figure up there near the bathroom window. It was pitch dark against the wall of the house.

He turned to glance up at the window of the sleeping room over the garage where Koku was supposed to spend the night. But Tom knew the giant was seldom there during the dark hours. He was as much of a night-prowler as a wildcat or an owl.

There was no light there in any case. But Koku did not use a light much. He could see in the dark, like a wild animal. Tom did not want to call him. If he must have Koku's help, he would have to climb the stairs to his bedside. The giant always aroused as wide awake as at noonday.

But while the young inventor hesitated a sudden, but muffled, snap--the breaking of metal--sounded. Tom knew instantly the direction from which the sound came.

Although he could see nothing up there at the bathroom window because of the rain and the deep shadow, he knew that the snapping sound meant the severing of the window lock that he had so recently closed. Some instrument had been forced under the bottom of the lower sash and pressure enough been brought to bear to break the thin steel lever.

On the heels of this sound came another. A muffled buzzing somewhere in the house--again! again! And then, startlingly clear from the room over the garage, the burglar alarm went off in Koku's chamber.

"It's all off now!" gasped Tom, and he ran to the foot of the honeysuckle ladder up which he knew the enemy had climbed to get to the roof of the porch. "If he comes down I'll have him!" muttered Tom, staring up into the mist and gloom.

"Fo' de lawsy's sake! 'Tain't mawnin', is it?" Rad's sleepy voice was heard to announce. "No, it's da'k as--" And the voice trailed off into silence.

"Tom! Tom!" the young fellow heard his aroused father shouting.

Tom knew that his father was in no danger. In fact Mr. Swift's voice did not even betray apprehension. It was. to the garage Tom looked for an explosion. But none came.

If Koku was up there the prolonged buzzing of the alarm did not awake him. Therefore he could not be there. Tom realized that if the burglar was to be taken the whole affair fell upon his shoulders.

"And I've got my hands full, if it is the fellow with the big feet that we saw on the Waterfield Road the other day," muttered the young inventor.

Nothing stirred on the porch roof. Moment after moment slipped by. Tom began to grow more than amazed. He was worried. What would happen next?

His father had not cried out again. Stepping around to the end of the roofed porch, Tom saw a light in Mr. Swift's room. Rad had evidently gone to sleep again. It would take more than an intermittent buzzer to rouse fully that colored man.

"When old Morpheus has a strangle hold on Rad, Gabriel's trump would scarcely awaken him," Tom muttered.

What had become of the enemy? If it was an ordinary burglar he would have feared the electric alarm instantly. The buzzers were still working. But there was no sign of the man who had set them off at the bathroom window.

Suddenly Tom heard a door slam. It was from the front of the house. Had his father come downstairs to look around and see what the matter was?

The young fellow started around the house on a run. He heard heavy bootsoles spurning the gravel of the path to the front gate. He arrived at the far corner of the house in time to see a man dash through the gateway and run down the street, disappearing finally into the fast-driving rain.

"Fooled me! He went in and right through and down the stairs! Out the front door!" gasped Tom. "Did he get anything? I wonder!"

He sprang up to the front porch and tried the door. It was locked again, of course. Should he ring the bell and get Rad or his father down to the door?

And then, of a sudden, the principal mystery of all this affair bit into Tom Swift's mind. The burglar had made his escape. He could relieve his father's anxiety later. It was his own puzzlement of mind that he first wished to ease.

Where was Koku?

Even had the giant been circling the stockade around the shops he surely must have come up to the home premises by this time. His keen ears could not fail to hear the buzzers. They were still going and would go until the switch was turned.

If the giant was in his room--Tom turned suddenly and started on a run for the rear premises. He still carried the hand-lamp and it lit his way into the garage door and up the narrow stairway. He shot the round beam of the lamp into Koku's room.

He had been obliged to have an iron bedstead made to order for the giant. It stood against one wall of the room. The buzzer was snarling like a huge bumblebee above the head of the couch. Below it sprawled the giant, eyes tightly closed and mouth slightly ajar. From the lips of Koku were emitted sounds worthy of Rad Sampson in his deepest slumbers!

"Asleep?" gasped Tom, stepping cat-like into the room.

And then he was suddenly aware of a sickish, heavy odor in the chamber. The window had been closed. But it was something more than stale air that Tom smelled.

A folded cloth lay on the floor beside the couch. The young fellow saw at once that it had been originally placed over the giant's face, but had slid off. And lucky for Koku that it had been dislodged!

"Chloroform!" muttered Tom. "He's drugged. It is no wonder he did not hear the burglar alarm."

In any event, the incident made one deep impression on Tom's mind. The spies who he believed were working for the Hendrickton & Western Railroad and its owner, Montagne Lewis, were desperate men. Tom could not believe that the fellow with the big feet was alone in Shopton and was unaided in his attempts to find out what Tom was doing.

This attempt to burglarize the house betrayed the caliber of the enemy. In chloroforming Koku he had taken the risk of murdering the giant. Only the fact that the pad of saturated cloth had fallen off Koku's face had, perhaps, saved the man from suffocation.

Tom did not tell the giant when he aroused what the matter with him was. Koku was ill enough! He was wrenched by interior spasms that seemed almost to tear his huge body to pieces.

"What done got into dat big lump o' bone an' grizzle?" demanded Eradicate. "He looks like, he swallowed a volcano, and it just got to wo'kin' right. My lawsy!"

"He is a sick man, all right," admitted Tom. "Looks like he wouldn't try to stab me to deaf wid no spear no mo'," went on Rad, inclined to approve of Koku's sufferings.

"If he died you'd be mighty sorry, old man," declared Tom, sternly.

"Sho' would. Be a mighty hard job to bury him," was the callous response.

Just the same, the crotchety old colored man began to hop around in lively fashion with hot water, and later with coffee and other stimulants; and he nursed Koku all day as though he were a big baby.

Koku, who had never been ill before in his life, was inclined to lay the trouble to an evil genius of some kind. Perhaps, in spite of his half-civilized state, he was still a devil- worshiper. At any rate, he had a vital respect for the forces of evil.

Naturally he considered this unknown and unexpected misery he suffered the result of malignant influences of some kind. Tom did not want him to suspect that the man with the big feet had any possible part in the mystery. Had Koku suspected this, and had he got his hands on the spy, the latter could never have been successfully used in that sort of work again. In all probability he would have said that he had had enough.

Meanwhile Tom made a point of considering each step he took alone thereafter with particular care. He had a bodyguard-- usually the giant after the latter had recovered--between the works and the house. He did not bring home any more the schedules or drawings connected with the electric locomotive that he proposed to have built and to test inside the stockade of the Swift Construction Company.

He even put a private detective to work on the matter of finding a man named Andy O'Malley who might be lurking around Shopton. He had a pretty clear description of the fellow, for he had not only seen him once, face to face by daylight, but Tom had written to the president of the H. & P. A. and had got from that gentleman a clear picture in words of the spy whom Mr. Bartholomew believed was working in the interests of Montagne Lewis.

"If O'Malley appears in Shopton, look out. He is a bad character. He is not only a notorious gunman, with several warrants out for him in these parts, but he is a cruel and desperate man in any event. The minute you mark him, have him arrested and telegraph me. We'll get him extradited and put him through for ten years or more right in this county." The private investigator, however, as the weeks went by, could not find any man who filled O'Malley's description.

Meanwhile Tom Swift had got what he called "a lead" and was working day and night upon the invention that he believed might make even the Jandel people respectful, if not a bit envious.

First of all Tom had arranged to have built all around inside the stockade a track of rails heavy enough to stand the wear and tear of the heaviest locomotive built. Meanwhile the various parts of his locomotive were being built in several shops, but would be shipped to the Swift Construction Company and assembled in Tom's try-out shed.

Great secrecy was of course maintained. Aside from the fact that the new invention had something to do with electric motive power, nobody about the shops could say what the new industry portended. Save, of course, the Swifts themselves, Ned Newton, and Mr. Damon, who was the Swifts' closest friend and sometimes had furnished additional capital for Tom's experiments.

There was a thing that Mr. Damon furnished Tom at this time that proved in the end to be of much importance. Before Tom had seized upon this idea of his eccentric friend, and had made proper use of it, something happened that came near to wrecking utterly Tom's invention and completely putting an end to Tom himself as an inventor.