especially as neither of us speaks Russian. We'll head south for another day and then— What's that?"

He paused and listened. From the distance came a dull drone of sound which brought him to his feet with a start. He raced out onto deck with Carnes at his heels. Far overhead in the blue, a tiny speck of black hovered.

"We're on the right trail, Carnes," he said grimly. The plane passed over them. In huge circles it sank toward the ground. Dr. Bird turned to Captain Evans. Orders flew from the bridge and a detail of marines rapidly stripped the covers from the two forward anti-aircraft rifles.

"I dislike to fire on that craft before it makes a hostile demonstration, Dr. Bird," demurred Captain Evans. "We are at peace with Russia. My action in firing might precipitate a war, or in any event, serious diplomatic misunderstandings."

"Allow me to correct you, Captain Evans, we are at war with Russia. The whole world is at war with the man who has pulled the earth out of her course. In any event, your orders are positive and the responsibility is mine. Wait until that plane gets within easy range and then shoot it down. Do not fail to get it; it must not get back to shore with word of our approach."

Captain Evans bowed gravely. Shells came up from the magazines and were piled by the guns. From the fire control stations came a monotonous calling of firing data. The guns slowly changed direction as the plane descended. Nearer and nearer it came, intent on positive identification of the war vessel below it. It passed over the Denver less than five thousand feet up. As it passed it swung off to one side and began to climb sharply. Dr. Bird glanced at the fighting top of the cruiser and swore softly. From the top the stars and stripes had been broken to the breeze.

"Fire at once!" he cried, "and then court-martial the fool who broke out that flag!"

The two three-inch rifles barked their message of death into the sky. For agonizing seconds nothing happened. The guns roared again. Below and behind the fleeing plane, two puffs of white smoke appeared in the sky. The staccato calls of the observers came from the control station and the guns roared again and again. Now above and now below the Russian plane appeared the white puffs that told of bursting shells, but the plane droned on, unharmed.

"It's away safely," groaned the doctor. "Now the fat is in the fire. Saranoff will know in an hour that we are coming. If we had a pursuit plane ready to take off, we might catch him, but we haven't. Oh, well, there's no use in crying over spilt milk. How soon will that amphibian be ready to take off?"

"In twenty minutes. Doctor," replied the Engineering Officer. "As soon as we finish filling the tanks and test the motor, she'll be ready to ramble."

"Hurry all you can. Hang a half dozen hundred-pound bombs and a few twenty-fives on the racks. Lower her over the side as soon as she's ready. Where's Lieutenant McCready?"

"Below, getting into his flying togs, Doctor."

"Good enough. Come on, Carnes, we'll go below and put on our fur-lined panties, too. We'll probably need them."

In half an hour the amphibian rose from the water. Lieutenant McCready was at the controls, with Carnes and the doctor at the bomb racks. The plane rose in huge spirals until the altimeter read four thousand feet. The pilot straightened it out toward the south. The plane was alone in the sky. For two hours it flew south and then veered to the east, following the line of the Gulf of Archangel. The town came in sight at last.

"Better drop down a couple of thousand, Lieutenant," said Dr. Bird into the speaking tube. "We can't see much from this altitude."

The plane swung around in a wide circle, gradually losing altitude. Carnes and the doctor hung over the side watching the ground below them. As they watched a puff of smoke came from a low building a mile from the edge of the town. Dr. Bird grabbed the speaking tube.

"Bank, McCready!" he barked, "They're firing at us."

The plane lurched sharply to one side. From a point a few yards below them and almost directly along their former line of flight, a burst of flame appeared in the air. The plane lurched and reeled as the blast of the explosion reached it. From other points on the ground came other puffs.

"Get out of here," shouted Dr. Bird. "There must be a dozen guns firing at us. One of them will have the range directly."

From all around them came flashes and the roar of explosions. The plane lurched and yawed in a sickening fashion. Lieutenant McCready fought heroically with the controls, trying to prevent the sideslips which were costing him altitude. Gradually the plane came under control and started to climb. The shells burst nearer as the plane took a straighter course and strove to fly out of the danger zone. Dr. Bird looked at the air-speed meter.

"A hundred and eighty," he shouted to Carnes. "We'll be safely out of range in a minute."

The bursts were mostly behind them now. Suddenly a blast of air struck them with terrific force. Half a dozen holes appeared in the fabric of the wings. A bit of high explosive shell plowed a way through the after compartment and wrecked the duplicate instrument board. In another moment they were out of range. Lieutenant McCready turned the nose of his plane toward the north.

"We came out of that well," cried Carnes. Dr. Bird dropped the speaking tube which he had held pressed to his ear and smiled grimly at the detective.

"I wish we had," he replied. "Our main gas tank is punctured."

An expression of alarm crossed the detective's face.

"Is it injured badly?" he asked.

"I don't know yet. McCready says that the gauge is dropping pretty rapidly. I'm going to go out and see what I can do."

"Can't I go, Doctor? I'm a good deal lighter than you are."

"You're not as strong or as agile, Carnes, and you haven't the mechanical ability to make the repair. Hand me that line."

He fastened one end of a coil of manila rope which Carnes handed him to his waist, while the detective fastened the other end to one of the safety belt hooks. With a word of farewell, he climbed out of the cockpit and onto a wing. In the pocket of his flying suit he carried a tool kit and repair material. Carnes shuddered as the doctor's figure disappeared under the plane. He snubbed the rope about a seat bracket and held it taut. For ten minutes the strain continued. It slackened at last, and the figure of the doctor reappeared on the wing. Slowly he climbed into the cockpit.

"I've made a temporary repair, Lieutenant," he called into the speaking tube, "and the leakage has stopped. How much gas have we left?"

"Enough for about an hour of flying, including the emergency tank."

"Thunder! No chance to get back to the Denver. Better head inland and follow the course of the Dwina. If we can locate the place we are looking for we may be able to drop a few eggs on it before we are washed out. In any event, it will be better to come down on land than on water."

McCready headed the plane south and followed the winding ribbon below him which marked the channel of the Dwina. He kept his altitude well over eight thousand feet. For a few minutes the plane roared along. Without warning the motor sputtered once or twice and died.

"Gas finished?" asked Dr. Bird into the speaking tube.

"No, there is plenty of gas for another forty-five minutes. It acted like a short in the wiring. Maybe another fragment got us that we didn't know about. I can glide to a safe landing, Doctor. Which direction shall I go?"

"It doesn't matter," replied Dr. Bird as he looked over the side. "Wait a minute, it does matter. See that long low building down there with the projection like a tower on top?