“Is the maneuver progressing as you wish. Dr. Bird?” asked the Chief of the Air Corps.

The famous scientist lowered his binoculars and smiled.

“Exactly, General,” he replied. “They are keeping a splendid line.”

“It is the greatest concentration of air force that this country has ever seen,” said General Merton proudly.

With a nod, Dr. Bird raised his glasses to his eyes and resumed his steady gaze. Five thousand feet below and two miles ahead of the huge transport plane which flew the flag of the Chief of the Air Corps, a long line of airplanes stretched away to the north and to the south. Six hundred and seventy-two planes, the entire First Air Division of the United States Army, were deployed in line at hundred-yard intervals, covering a front of nearly forty miles. Fifteen hundred feet above the ground, the line roared steadily westward over Maryland at ninety miles an hour. At ten-second intervals, a puff of black dust came from a discharge tube mounted on the rear of each plane. The dust was whirled about for a moment by the exhaust, and then spread out in a thin layer, marking the path of the fleet.

“I hope the observers on the planes are keeping careful notes of the behavior of those dust clouds,” said Dr. Bird after an interval of silence. “We are crossing the Chesapeake now, and things may start to happen at any moment.”

“They’re all on their toes, Doctor,” replied General Merton. “I understood in a general way from the President that we are gathering some important meteorological data for you, but I am ignorant of just what this data is. Is it a secret?”

Dr. Bird hesitated.

“Yes,” he said slowly, “it is. However, I can see no reason why this secret should not be entrusted to you. We are seeking a means of ending the great drought which has ravaged the United States for the past two years.”

Before General Merton had time to make a reply, his executive officer hastened forward from the radio set which was in constant communication with the units of the fleet.

“Two of the planes on the north end of the line are reporting engine trouble, sir,” he said.

Dr. Bird dropped his glasses and sat bolt upright.

“What kind of engine trouble?” he demanded sharply.

“Their motors are slowing down for no explainable reason. I can’t understand it.”

“Are their motors made with sheet steel cylinders or with duralumin engine blocks?”

“Sheet steel.”

“The devil! I hadn’t foreseen this, although it was bound to happen if my theory was right. Tell them to climb! Climb all they know! Don’t let them shut off their motors for any reason, unless they are about to crash. Turn this ship to the north and have the pilot climb--fast!”

A nod from General Merton confirmed the doctor’s orders. The line of planes kept on to the west, but the flagplane turned to the north and climbed at a sharp angle, her three motors roaring at full speed. With the aid of binoculars, the two ships in trouble could be picked out, falling gradually behind the line. They were flying so slowly that it seemed inevitable that they would lose flying speed and crash to the ground.

“More speed!” cried the doctor. “We’ve elevation enough!”

The altimeter stood at eight thousand feet when the pilot leveled out the flagplane and tore at full speed toward the laboring ships. The main fleet was twenty miles to the west.

They were almost above the point where the two planes had first began to slow down. As they winged along, the three motors of the flagplane took on a different note. It was a laboring note, pitched on a lower scale. Gradually the air-speed meter of the ship began to show a lower reading.

“Locate us on the map, Carnes!” snapped Dr. Bird.

Operative Carnes of the United States Secret Service bent over a large-scale map of Maryland, spread open on a table. With the aid of the navigating officer, he spotted on the map the point over which the plane was flying.

“There goes Burleigh’s ship!” cried the executive officer.

There was a gasp from the occupants of the flagplane’s cabin. Far below them, one of the crippled planes had slowed down until it had lost flying speed. Whirling like a leaf, it plunged toward the ground. Two small specks detached themselves from the falling mass. They hovered over the falling plane for an instant. Suddenly a patch of white appeared in the air, and then another. The two specks fell more slowly.

“Good work!” exclaimed General Merton. “They took to their ‘chutes just in time.”

“We’ll be taking them in a few minutes if our motors don’t pick up!” replied the executive officer.

Far below them, the doomed plane crashed to the ground. As it struck there was a blinding flash followed by vivid flames as the gasoline from the bursted tank ignited. The two members of the crew were drifting to the east as they fell. It was evident that they were in no danger.

“Where is Lightwood’s plane?” asked General Merton anxiously.

“It’s still aloft and making its way slowly north. He intends to try for an emergency landing at the Aberdeen Proving Ground field,” replied the executive officer.

“That’s where we had better head for,” said Dr. Bird. “I hope that the charge on Captain Lightwood’s plane discharges through the tail skid when he lands. If it doesn’t, he’ll be in serious danger. Follow him and we’ll watch.”

Five thousand feet below them, the crippled plane limped slowly along toward Aberdeen. It was gradually losing elevation. Two specks suddenly appeared in the air, followed by white patches as the parachutes opened. Captain Lightwood and his gunner had given up the unequal fight and taken to the air. As the ship struck the ground, again there was a blinding flash, followed by an inferno of roaring flames.

“We’re not in much better shape than they were, General,” said the executive officer as he came back from the control room where the pilots were heroically striving to keep their motors turning over fast enough to keep up flying speed. “We’d better get into our ‘chutes.”

“The Proving Ground is just ahead,” said the doctor. “Can’t we make it by sacrificing our elevation?”

“We’re trying to do that, Doctor, but we’re down to four thousand now and falling fast. Get ready to jump.”

Dr. Bird buckled on the harness of the pack parachute which the executive officer offered him. The rest of the crew had hurriedly donned their packs and stood ready.

For another five minutes the plane struggled on. Suddenly a large flat expanse of open ground which had been in sight for some time, seemed to approach with uncanny rapidity.

“There’s the landing field!” cried the General. “We’ll make it yet!”

Lower and lower the plane sank with the landing field still too far away for comfort. The pilot leveled off as much as he dared and drove on. The motors were laboring and barely turning over at idling speed. They passed the nearer edge of the field with the flagplane barely thirty feet off the ground. In another moment the wheels touched and the plane rolled to a halt.

“Don’t get out!” cried Dr. Bird.

He looked around the cabin and picked up a coil of bare antenna wire which hung near the radio set. He wrapped one end of the wire around the frame of the plane. To the other end, he attached his pack ‘chute.

“Open the door!” he cried.

As the door swung open, he threw the ‘chute out toward the ground. As it touched, there was a blinding flash, followed by a report which shook the plane. A strong odor of garlic permeated the air.

“All right!” cried the doctor cheerfully. “All out for Aberdeen. The danger is past.”

He set the example by jumping lightly from the plane. General Merton followed more slowly, his face white and his hands shaking.

“What was it, Doctor,” he asked. “I have been flying since 1912, yet I have never seen or heard of anything like that.”

“Just a heavy charge of static electricity,” replied the doctor. “That was what magnetized your cylinder walls and your piston rings and slowed your motors down. It was the same thing that wrecked those two ships. Unless it leaks off, the men of some of your other ships are due to get a nasty shock when they land to-night. I discharged the charge we had collected through a ground wire. Here comes a car, we’ll go up to Colonel Wesley’s office. Carnes, you have these maps?”

“Surely, Doctor.”

“All right, let’s go.”

“But what about this ship, Doctor?” objected the General. “Can’t something be done about it?”

“Certainly. I hadn’t forgotten it. Have your crew stand by. I’ll telephone Washington and have some men with apparatus sent right down from the Bureau of Standards. They’ll have it ready for flying in the morning. We’ll also have search parties sent out in cars to locate the crews of those abandoned ships and bring them in. Now let’s go.”

Colonel Wesley, the commanding officer of the Aberdeen Proving Ground, welcomed Carnes and Dr. Bird warmly.

“I’ll tell you, General Merton,” he said to the Chief of the Air Corps, “if you ever get up against something that is beyond all explanation, you want to get these two men working on it. They are the ones who settled that poisoning case here, you know.”

“Yes, I read of that,” replied the general. “I am inclined to think that they are up against something even queerer right now.”

Colonel Wesley’s eyes sparkled.

“Give your orders, Dr. Bird!” he cried. “Since our last experience with you, you can’t give an order on this post that won’t be obeyed!”

“Thank you, Colonel,” said Dr. Bird warmly. “One reason why I came here was that I knew that I could count on your hearty cooperation. The first thing I want is two cars. I want them sent out to bring in the crews of two ships which were abandoned some eight miles south of here. Carnes will locate them on the map for your drivers.”

“They’ll be ready to start in five minutes, Doctor. What next?”

“Turn out every man and every piece of transportation you have to-morrow morning. I want the men armed. They will have to search a stretch of swamp south of here, inch by inch, until they find what I’m looking for.”

“They’ll be ready, Doctor. Would it be indiscreet for me to ask what it’s all about?”

“Not at all, Colonel. I was about to explain to General Merton when trouble started. I am searching for the cause of the great drought which has been afflicting this country for the past two years. If I can find the cause, I hope to end it.”

“Oh! I had a sneaking hope that we were in for another skirmish with that Russian chap, Saranoff, whose men started that poison here.”

“I rather think we are, Colonel Wesley.”

General Merton laughed.

“I’ll swallow a good deal, Dr. Bird,” he said, “but when you talk of an individual being responsible for the great drought, it’s a little too much. A man can’t control the weather, you know!”

“Yet a man, or an incarnate devil--I don’t know which he is--did control the weather once, as well as the sun. But for the humble efforts of two Americans, aided by a Russian girl whose brother Saranoff had murdered, he might be still controlling it.”

General Merton was silent now.

“Carnes, let me have that map,” went on the doctor. When the detective had unrolled a map of the United States on Colonel Wesley’s table, Dr. Bird continued, pointing to the map as he spoke.

“On this map,” he said, “is plotted the deficiency in rainfall for the past year, from every reporting station in the United States. These red lines divide the country into areas of equal deficiency. The area most affected, as you can see, is longer east and west, than it is north and south. It is worst in the east, in fact in this very neighborhood. Even a casual glance at the map will show you that the center of the drought area, from an intensity standpoint, lies in Maryland, a few miles south of here.”

“In fact, just about where those two planes went down,” added Carnes.

“Precisely, old dear. That was why we went over that section with the fleet. Now, gentlemen, note a few other things about this drought. The areas of drought follow roughly the great waterways, the Ohio and the Potomac valleys being especially affected. In other words, the drought follows the normal air currents from this point. If something were to be added to the air which would tend to prevent rain, it would in time drift, just as the drought areas have drifted.”

General Merton and Colonel Wesley bent over the map.

“I believe you’re right, Doctor,” admitted the general.

“Thank you. The President was convinced that I was before he placed the First Air Division under my orders. Frankly, that search was the real object of assembling the fleet. The maneuvers are a mere blind.”

General Merton colored slightly.

“Now, I’ll try to give you some idea of what I think is the method being used,” went on the doctor, ignoring General Merton’s rising color. “In the past, rain has been produced in several cases where conditions were right--that is, when the air held plenty of moisture which refused to fall--by the discharge from a plane of a cloud of positively charged dust particles. Ergo, a heavy negative charge in the air, which will absorb rather than discharge a positive charge, should tend to prevent rain from falling. I believe that a stream of negative particles is being liberated into the air near here, and allowed to drift where it will. That was my theory when I had the First Air Division equipped with those dust ejector tubes.

“I knew that if such a condition existed, the positively charged dust would be pulled down toward the source of the negative particle stream, which must, in many ways, resemble a cathode ray. That was why I wanted the behavior of the dust clouds watched and reported. What I did not foresee was that the iron and steel parts of the plane, accumulating a heavy negative charge, would be magnetized enough to slow down the motors and eventually wreck the ships.”

“We have had eight ships wrecked unexplainably within twenty miles of here, all of them to the south, during the past year,” said Colonel Wesley.

“It had slipped my notice. At any rate, the behavior of the ships this afternoon showed me that my theory is correct, and that some such device exists and is in active operation. Our next task is to locate it and destroy it.”

“You shall have every man on the Proving Ground!” cried Colonel Wesley.

“Thank you. General Merton, will you detach three ships from the First Air Division by radio and have them report here? I want two pursuit ships and one bomber, with a rack of hundred-pound demolition bombs. All three must have duralumin cylinder blocks.”

“I’ll do it at once, Doctor,” the general agreed.

“Thank you. Carnes, telephone Washington for me. Tell Dr. Burgess that I want Tracy, Fellows and Von Amburgh, with three more men down here by the next train. Also tell him to have Davis rig up a demagnetizer large enough to demagnetize the motors of a transport plane and bring it down here to fix up General Merton’s ship. When you have finished that, get hold of Bolton and ask for a dozen secret service men. I want selected men with Haggerty in charge.”

“All right, Doctor. Shall I tell Miss Andrews to come down as well?”

Dr. Bird frowned.

“Certainly not. Why would she come down here?”

“I thought she might be useful, Doctor.”

“Carnes, as you know, I dislike using women because they can’t control their emotions or their expressions. She would just be in the way.”

“It seems to me that she saved both our lives in Russia, Doctor, and but for her, you wouldn’t have come out so well in your last adventure on the Aberdeen marshes.”

“She did the first through uncontrolled emotions, and the second through a flagrant disobedience of my orders. No, don’t tell her to come. Tell her not to come if she asks.”

Carnes turned away, but hesitated.

“Doctor, I wish you’d let me have her come down here. I didn’t trust her at first when you did, but she has proved her loyalty and worth. Besides, I don’t like the idea of leaving her unguarded in Washington with you and me down here, and with Haggerty coming down.”

Dr. Bird looked thoughtful.

“There’s something in that, Carnes,” he reflected. “All right, tell her to come along, but remember, she is not in on this case. She is being brought here merely for safety, not to mix up in our work.”

“Thanks, Doctor.”

The detective returned in ten minutes with a worried expression.

“She wasn’t in your office, Doctor,” he reported.

“Who? Oh, Thelma. Where was she?”

“No one seems to know. She left yesterday afternoon and hasn’t returned.”

“Oh, well, since I am out of the city, I expect she decided to take a vacation. Women are always undependable. Did you get hold of the rest?”

“They’ll be down at midnight, all but Davis. He’ll come down in the morning.”

“Good enough! Now, Colonel, if you’ll have the officers who are going out to-morrow assembled, we’ll divide the territory and make our plans for the search.”

A week later, the situation was unchanged. Secret service operatives and soldiers from the Proving Ground had covered, foot by foot, square miles of territory south of the Proving Ground, but without result. Not a single unexplainable thing had been found. Sensitive instruments sent down from the Bureau of Standards, instruments so sensitive that they would detect an electric light burning a mile away, had yielded no results. As a final measure, General Merton had ordered a dozen planes with steel-cylindered motors to the Proving Ground and they had repeatedly crisscrossed the suspected territory, but had acquired no static charge large enough to affect them. It was evident that Saranoff’s device, if it existed, had been moved, or else was not in operation.

Also, to Carnes’ openly expressed and Dr. Bird’s secret worry, Thelma Andrews had not returned to the Bureau of Standards. The Russian girl, formerly known as Feodrovna Androvitch, a tool and follower of Ivan Saranoff, had acted with Carnes and the doctor in their long drawn-out fight with the arch-communist often enough to be a marked woman.

Urged by Carnes, Bolton, the head of the Secret Service, put a dozen of his best men on her trail, but they found nothing. She had disappeared as thoroughly as if the earth had opened and swallowed her up. At last, as the combing of the Aberdeen marshes yielded no results, Dr. Bird acceded to Carnes’ request, and the detective left for Washington to take personal charge of the search. Dr. Bird sat alone in his quarters at the Officers’ Club, futilely wracking his brains for a clue to his further procedure.

The telephone rang loudly. With a grunt, he took down the receiver.

A feminine voice spoke with a strong foreign accent.

“I vant der Herr Doktor Vogel, plees!”

“You want who? Oh, yes. Vogel--bird! This is Dr. Bird speaking.”

The voice instantly lost both its foreign accent and its guttural quality.

“I thought so when you spoke, Doctor, but I wanted to make sure. This is Thelma Andrews.”

“Where the devil have you been? Half the Secret Service is looking for you, including Carnes, who deserted me and is in Washington.”

“He is? I’m sorry. Listen, Doctor, it’s a long story and I can’t go into details now. I got a clue on the day you left. As I couldn’t get in touch with you, I followed it myself. I’ve located Saranoff’s main base in the Bush River marshes.”

“You have! Where is it?”

“It’s underground and you’ve passed over it a dozen times during the past week. It’s unoccupied now and the machines are idle until your search is over. I know the way to it. If you’ll join me now, we can get in and hopelessly wreck the device in a short time. To-morrow you can bring your men down here and take charge of it.”

Dr. Bird’s eyes glistened.

“I’ll come at once, Thelma!” he cried. “Where are you?”

“I’m down on Romney Creek. Come down to the Water Impact Range below Michaelville, and I’ll meet you at the wharf. You’d better come alone, because we’ll have to sneak.”

“Good for you!” cried the doctor. “I’ll be down in an hour.”

“All right, Doctor. I’ll be waiting for you.”

At Michaelville, Dr. Bird left his car and stepped on the scooter which ran on the narrow gauge track connecting the range house with the wharf on Romney Creek. He started it with no difficulty and it coughed away into the night. For three and a half miles, nothing broke the monotony of the trip. Dr. Bird, his hand on the throttle, kept his eyes on the twin ribbons of steel which slid along under the headlight. The road made a sharp turn and emerged from the thick wood through which it had been traveling. Hardly had the lights shot along the track in the new direction than Dr. Bird closed the throttle and applied the brakes rapidly. A heavy barricade of logs was piled across the track.

The doctor pressed home on the brake lever until the steel shoes screamed in protest, but no brakes could bring the heavy scooter to a stop as swiftly as was needful to avoid a crash. It was still traveling at a good rate of speed when it rammed into the barricade and overturned.

Dr. Bird was thrown clear of the wrecked scooter. He landed on soft mud beside the track. As he strove to rise, the beam of a flashlight struck him in the eyes and a guttural, sneering voice spoke through the darkness.

“Don’t move, Dr. Bird. It will be useless and will only lead to your early death, a thing I should regret.”

“Saranoff!” cried Dr. Bird.

“I am flattered, Doctor, that you know my voice. Yes, it is I, Ivan Saranoff, the man whom you have so often foiled. You drove me from America and tried to bar the road against my return, but I only laughed at your efforts. I returned here only for one purpose, to capture you and to compass your death.”

Dr. Bird rose to his feet and laughed lightly.

“You’ve got me, Saranoff,” he said, “but the game isn’t played out yet. I represent an organization which won’t end with my death, you know.”

A series of expletives in guttural Russian answered him. In response to a command from their leader, two men came forward and searched the doctor quickly and expertly, removing the automatic pistol which he carried under his left armpit.

“As for your organization, as you call it--pouf!“ said the Russian scornfully. “Carnes, a brainless fool who does only as you tell him, a few half-wits in the Bureau of Standards, some of them already in my pay, and one renegade girl. She shall learn what it means to betray the Soviets and their leader.”

“You’ll have to catch her first,” replied Dr. Bird, a sardonic grin on his face.

“I have but to snap my fingers and she will come whining back, licking my hand and imploring mercy,” boasted the Russian. “Bring him along!”

TWO men approached and Seized the doctor by his arms. Dr. Bird shook them off contemptuously.

“Keep your filthy paws off me!” he cried. “I know when I’m bested, and I’ll come quietly, but I won’t be dragged.”

The men looked at their leader for orders. From behind his light, the Russian studied his opponent. He gave vent to a stream of guttural Russian. The men fell back.

“For your information, Doctor,” he said in a sneering tone. “I have told my men to follow you closely, gun in hand. At the slightest sign of hesitation, or at the first attempt to escape, they will fire. They are excellent shots.”

“Lead on, Saranoff,” was Dr. Bird’s cheery comment.

With a shrug of his shoulders, the leader of the Young Labor party turned and made his way along the track toward the wharf. Dr. Bird looked anxiously ahead as they approached, fearing that Feodrovna Androvitch would be discerned in her hiding place. Saranoff correctly interpreted his gaze.

“Does der Herr Doktor Vogel eggspect somevun?” he asked in the voice which had first come over Dr. Bird’s telephone. The doctor started and the Russian went on in the voice of the doctor’s secretary. “I’m so glad you came, Dr. Bird. I am going to take you directly to the main base of our dearly beloved friend, Ivan Saranoff.”