It is an unwritten law of all flying services that when an enemy machine bursts into flames in the course of an aerial combat the aggressor who has brought the catastrophe should leave well enough alone and allow his stricken enemy to fall unmolested.

Lieutenant Callendar, returning from a great and enjoyable strafe, was met by three fast scouts of the Imperial German Flying Service. He shot down one, when his gun was jammed. He banked over and dived to avoid the attentions of the foremost of his adversaries, but was hit by a chance bullet, his petrol tank was pierced and he suddenly found himself in the midst of noisy flames which said "Hoo-oo-oo!"

As he fell, to his amazement and wrath, one of his adversaries dropped after him, his machine-gun going like a rattle. High above the combatants a fourth and fifth machine, the one British and the other a unit of the American squadron, were tearing down-skies. The pursuing plane saw his danger, banked round and sped for home, his companion being already on the way.

"Ye're no gentleman," said Tam grimly, "an' A'm goin' to strafe ye!"

Fortunately for the flying breaker of air-laws, von Bissing's circus was performing stately measures in the heavens and as von Bissing's circus consisted of ten very fast flying-machines, Tam decided that this was not the moment for vengeance and came round on a hairpin turn just as von Bissing signaled, "Attack!"

Tam got back to the aerodrome to discover that Callendar, somewhat burnt but immensely cheerful, was holding an indignation meeting, the subject under discussion being "The Game and How It Should Be Played."

"The brute knew jolly well I was crashing. It's a monstrous thing!"

"One was bound to meet fellows like that sooner or later," said Captain Blackie, the squadron commander, philosophically. "I suppose the supply of gentlemen does not go round, and they are getting some rubbish into the corps. One of you fellows drop a note over their aerodrome and ask them what the dickens they mean by it. Did you see him, Tam?"

"A' did that," said Tam; "that wee Hoon was saved from destruction owing to circumstances ower which A' had no control. A' was on his tail; ma bricht-blue eyes were glancin' along the sichts of ma seelver-plated Lewis gun, when A' speered the grand circus of Mr. MacBissing waiting to perform."

Tam shook his head.

"A'm hoping," said he, "that it was an act of mental aberration, that 'twas his first crash; and, carried away by the excitement and enthusiasm of the moment, the little feller fell into sin. A'm hoping that retribution is awaiting him.

"'Ma wee Hindenburg,' says Mr. MacBissing, stern and ruthless, 'did I no see ye behavin' in a manner likely to bring discredit upon the Imperial and All-Highest Air Sairvice of our Exalted and Talkative Kaiser? Hoch! Hoch! Hoch!'

"Little Willie Hindenburg hangs his heid.

"'Baron,' or 'ma lord,' as the case may be, says he, 'I'll no be tellin' ye a lie. I was not mesel'! That last wee dram of sauerkraut got me all lit up like a picture palace!' says he; 'I didn't know whether it was on ma heid or somebody else's,' says he; 'I'll admit the allegation and I throw mesel' on the maircy o' the court.'

"'Hand me ma strop,' says MacBissing, pale but determined, and a few minutes later a passer-by micht have been arrested and even condemned to death by hearin' the sad and witchlike moans that came frae headquarters."

That "Little Willie Hindenburg" had not acted inadvertently, but that it was part of his gentle plan to strafe the strafed—an operation equivalent to kicking a man when he is down—was demonstrated the next morning, for when Thornton fell out of control, blazing from engine to tail, a German flying-man, unmistakably the same as had disgraced himself on the previous day, came down on his tail, keeping a hail of bullets directed at the fuselage, though he might have saved himself the trouble, for both Thornton and Freeman, his observer, had long since fought their last fight.

Again Tam was a witness and again, like a raging tempest, he swept down upon the law-breaker and again was foiled by the vigilant German scouts from executing his vengeance.

Tam had recently received from home a goodly batch of that literature which was his peculiar joy. He sat in his bunk on the night of his second adventure with the bad-mannered airman, turned the lurid cover of "The Seven Warnings: The Story of a Cowboy's Vengeance," and settled himself down to that "good, long read" which was his chiefest and, indeed, his only recreation. He began reading at the little pine table. He continued curled up in the big armchair—retrieved from the attic of the shell-battered ChÂteau d'Enghien. He concluded the great work sitting cross-legged on his bed, and the very restlessness which the story provoked was a sure sign of its gripping interest.

And when he had finished the little work of thirty-two pages, he turned back and read parts all over again, a terrific compliment to the shy and retiring author. He closed the book with a long sigh, sat upon his bed for half an hour and then went back to the pine table, took out from the dÉbris of one of the drawers a bottle of ink, a pen and some notepaper and wrote laboriously and carefully, ending the seven or eight lines of writing with a very respectable representation of a skull and cross-bones.

When he had finished, he drew an envelope toward him and sat looking at it for five minutes. He scratched his head and he scratched his chin and laid down his pen.

It was eleven o'clock, and the mess would still be sitting engaged in discussion. He put out the light and made his way across the darkened aerodrome.

Blackie saw him in the anteroom, for Tam enjoyed the privilege of entrÉe at all times.

"His name? It's very curious you should ask that question, Tam," smiled Blackie; "we've just had a message through from Intelligence. One of his squadron has been brought down by the Creepers, and they are so sick about him that this fellow who was caught by the Creepers gave him away. His name is von Mahl, the son of a very rich pal of the Kaiser, and a real bad egg."

"Von Mahl," repeated Tam slowly, "and he will be belongin' to the Roulers lot, A'm thinkin'?"

Blackie nodded.

"They complain bitterly that he is not a gentleman," he said, "and they would kick him out but for the fact that he has this influence. Why did you want to know?"

"Sir-r," said Tam solemnly, "I ha'e a grand stunt."

He went back to his room and addressed the envelope:

"Mr. von Mahl."

The next morning when the well-born members of the Ninety-fifth Squadron of the Imperial German Air Service were making their final preparations to ascend, a black speck appeared in the sky.

Captain Karl von Zeiglemann fixed the speck with his Zeiss glasses and swore.

"That is an English machine," he said; "those Bavarian swine have let him through. Take cover!"

The group in the aerodrome scattered.

The Archie fire grew more and more furious and the sky was flecked with the smoke of bursting shell, but the little visitor came slowly and inexorably onward. Then came three resounding crashes as the bombs dropped. One got the corner of a hangar and demolished it. Another burst into the open and did no damage, but the third fell plumb between two machines waiting to go up and left them tangled and burning.

The German squadron-leader saw the machine bank over and saw, too, something that was fluttering down slowly to the earth. He called his orderly.

"There's a parachute falling outside Fritz. Go and get it."

He turned to his second in command.

"We shall find, MÜller, that this visitor is not wholly unconnected with our dear friend von Mahl."

"I wish von Mahl had been under that bomb," grumbled his subordinate. "Can't we do something to get rid of him, Herr Captain?"

Zeiglemann shook his head.

"I have suggested it and had a rap over the knuckles for my pains. The fellow is getting us a very bad name."

Five minutes later his orderly came to the group of which Zeiglemann was the center and handed him a small linen parachute and a weighted bag. The squadron-leader was cutting the string which bound the mouth of the bag when a shrill voice said:

"Herr Captain, do be careful; there might be a bomb."

There was a little chuckle of laughter from the group, and Zeiglemann glowered at the speaker, a tall, unprepossessing youth whose face was red with excitement.

"Herr von Mahl," he snapped with true Prussian ferocity, "the air-services do not descend to such tricks nor do they shoot at burning machines."

"Herr Captain," spluttered the youth, "I do what I think is my duty to my Kaiser and my Fatherland."

He saluted religiously.

To this there was no reply, as he well knew, and Captain Zeiglemann finished his work in silence. The bag was opened. He put in his hand and took out a letter.

"I thought so," he said, looking at the address; "this is for you, von Mahl." He handed it to the youth, who tore open the envelope.

They crowded about him and read it over his shoulder:

It was signed with a skull and cross-bones.

The young man looked bewildered from one to the other. Every face was straight.

"What—what is this?" he stammered; "is it not absurd? Is it not frivolous, Herr Captain?"

He laughed his high, shrill little laugh, but nobody uttered a sound.

"This is serious, of course, von Mahl," said Zeiglemann soberly. "Although this is your private quarrel, the squadron will do its best to save you."

"But, but this is stupid foolishness," said von Mahl as he savagely tore the note into little pieces and flung them down. "I will go after this fellow and kill him. I will deal with this Herr Tam."

"You will do as you wish, Herr von Mahl, but first you shall pick up those pieces of paper, for it is my order that the aerodrome shall be kept clean."

Tam swooped back to his headquarters in time for breakfast and made his report.

"The next time you do tricks over Roulers they'll be waiting for you, Tam," said Blackie with a shake of his head. "I shouldn't strain that warning stunt of yours."

"Sir-r," said Tam, "A've no intention of riskin' government property."

"I'm not thinking of the machine, but of you."

"A' was thinkin' the same way," said Tam coolly. "'Twould be a national calamity. A' doot but even the Scotsman would be thrown into mournin'—'Intelligence reaches us,' says our great contempor'y, 'from the Western Front which will bring sorrow to nearly every Scottish home reached by our widely sairculated journal, an' even to others. Tam the Scoot, the intreepid airman, has gone west. The wee hero tackled single-handed thairty-five enemy 'busses, to wit, Mr. MacBissing's saircus, an' fell, a victim to his own indomitable fury an' hot temper, after destroyin' thairty-one of the enemy. Glascae papers (if there are any) please copy.'"

That Blackie's fears were well founded was proved later in the morning. Tam found the way to Roulers barred by an Archie barrage which it would have been folly to challenge. He turned south, avoiding certain cloud masses, and had the gratification of seeing "the circus" swoop down from the fleece in a well-designed encircling formation.

Tam swung round and made for Ypres, but again found a barring formation.

He turned again, this time straight for home, dropping his post-bag (he had correctly addressed his letter and he knew it would be delivered), shot down out of control a diving enemy machine that showed fight, chased a slow "spotter" to earth, and flashed over the British trenches less than two hundred feet from the ground with his wings shot to ribbons—for the circus had got to within machine-gun range.

A week later Lieutenant von Mahl crossed the British lines at a height of fifteen hundred feet, bombed a billet and a casualty clearing station and dropped an insolent note addressed to "The Englishman Tamm." He did not wait for an answer, which came at one o'clock on the following morning—a noisy and a terrifying answer.

"This has ceased to be amusing," said Captain von Zeiglemann, emerging from his bomb-proof shelter, and wired a requisition for three machines to replace those "destroyed by enemy action," and approval for certain measures of reprisal. "As for that pig-dog von Mahl...."

"He has received his fifth warning," said his unsmiling junior, "and he is not happy."

Von Mahl was decidedly not happy. His commandant found him rather pale and shaking, sitting in his room. He leaped up as von Zeiglemann entered, clicked his heels and saluted. Without a word the commandant took the letter from his hand and read:

"So!" was von Zeiglemann's comment.

"It is rascality! It is monstrous!" squeaked the lieutenant. "It is against the rules of war! What shall I do, Herr Captain?"

"Go up and find Tam and shoot him," said Zeiglemann dryly. "It is a simple matter."

"But—but—do you think—do you believe—?"

Zeiglemann nodded.

"I think he will keep his word. Do not forget, Herr Lieutenant, that Tam brought down von MÜller, the greatest airman that the Fatherland ever knew."

"Von MÜller!"

The young man's face went a shade paler. The story of von MÜller and his feud with an "English" airman and of the disastrous sequel to that feud, was common knowledge throughout Germany.

Walking back to Command Headquarters, von Zeiglemann expressed his private views to his confidant.

"If Tam can scare this money-bag back to Frankfurt, he will render us a service."

"He asked me where I thought he would be safe—he is thinking of asking for a transfer to the eastern front," said Zeiglemann's assistant.

"And you said—"

"I told him that the only safe place was a British prison camp."

"Please the good God he reaches there," said Zeiglemann piously, "but he will be a fortunate man if he ever lands alive from a fight with Tam. Do not, I command you, allow him to go up alone. We must guard the swine—keep him in the formation."

Von Zeiglemann went up in his roaring little single-seater and ranged the air behind the German lines, seeking Tam. By sheer luck he was brought down by a chance Archie shell and fell with a sprained ankle in the German support-trenches, facing Armentiers.

"A warning to me to leave Mahl to fight his own quarrels," he said as he limped from the car which had been sent to bring him in.

There comes to every man to whom has been interpreted the meaning of fear a moment of exquisite doubt in his own courage, a bewildering collapse of faith that begins in uneasy fears and ends in blind panic.

Von Mahl had courage—an airman can not be denied that quality whatever his nationality may be—but it was a mechanical valor based upon an honest belief in the superiority of the average German over all—friends or rivals.

He had come to the flying service from the Corps of the Guard; to the Corps of the Guard from the atmosphere of High Finance, wherein men reduce all values to the denomination of the mark and appraise all virtues by the currency of the country in which that virtue is found.

His supreme confidence in the mark evaporated under the iron rule of a colonel who owned three lakes and a range of mountains and an adjutant who had four surnames and used them all at once.

His confidence in the superiority of German arms, somewhat shaken at Verdun, revived after his introduction to the flying service, attained to its zenith at the moment when he incurred the prejudices of Tam, and from that moment steadily declined.

The deterioration of morale in a soldier is a difficult process to reduce to description. It may be said that it has its beginnings in respect for your enemy and reaches its culminating point in contempt for your comrades. Before you reach that point you have passed well beyond the stage when you had any belief in yourself.

Von Mahl had arrived at the level of descent when he detached himself from his comrades and sat brooding, his knuckles to his teeth, reviewing his abilities and counting over all the acts of injustice to which he had been subjected.

Von Zeiglemann, watching him, ordered him fourteen days' leave, and the young officer accepted the privilege somewhat reluctantly.

There was a dear fascination in the danger, he imagined. He had twice crossed fire with Tam and now knew him, his machine, and his tactics almost intimately.

Von Mahl left for Brussels en route for Frankfurt and two days later occurred one of those odd accidents of war which have so often been witnessed.

Tam was detailed to make one of a strong raiding party which had as its objective a town just over the Belgian-German frontier. It was carried out successfully and the party was on its way home when Tam, who was one of the fighting escort, was violently engaged by two machines, both of which he forced down. In the course of a combat he was compelled to come to within a thousand feet of the ground and was on the point of climbing when, immediately beneath him, a long military railway train emerged from a tunnel. Tam carried no bombs, but he had two excellent machine guns, and he swooped joyously to the fray.

A few feet from the ground he flattened and, running in the opposite direction to that which the train was taking, he loosed a torrent of fire into the side of the carriages.

Von Mahl, looking from the window of a first-class carriage, saw in a flash the machine and its pilot—then the windows splintered to a thousand pieces and he dropped white and palpitating to the floor.

He came to Frankfurt to find his relations had gone to Karlsruhe, and followed them. The night he arrived Karlsruhe was bombed by a French squadron.... von Mahl saw only a score of flying and vengeful Tams. He came back to the front broken in spirit and courage. "The only place you can be safe is an English internment camp."

He chewed his knuckles with fierce intentness and thought the matter over.

"A'm delayin' ma seventh warnin'," said Tam, "for A'm no' so sure that McMahl is aboot. A've no' seen the wee chiel for a gay lang time."

"Honestly, Tam," said young Craig (the last of the Craigs, his two brothers having been shot down over Lille), "do you really think you scare Fritz?"

Tam pulled at his cigar with a pained expression, removed the Corona from his mouth, eyeing it with a disappointed sneer, and sniffed disparagingly before he replied.

"Sir-r," he said, "the habits of the Hoon, or Gairman, ha'e been ma life study. Often in the nicht when ye gentlemen at the mess are smokin' bad seegairs an' playin' the gamblin' game o' bridge-whist, Tam o' the Scoots is workin' oot problems in Gairman psych—I forget the bonnie waird. There he sits, the wee man wi'oot so much as a seegair to keep him company—thank ye, sir-r, A'll not smoke it the noo, but 'twill be welcomed by one of the sufferin' mechanics—there sits Tam, gettin' into the mind, or substitute, of the Hoon."

"But do you seriously believe that you have scared him?"

Tam's eyes twinkled.

"Mr. Craig, sir-r, what do ye fear wairst in the world?"

Craig thought a moment.

"Snakes," he said.

"An' if ye wanted to strafe a feller as bad as ye could, would ye put him amongst snakes?"

"I can't imagine anything more horrible," shuddered Craig.

"'Tis the same with the Hoon. He goes in for frichtfulness because he's afraid of frichtfulness. He bombs little toons because he's scairt of his ain little toons bein' bombed. He believes we get the wind up because he'd be silly wi' terror if we did the same thing to him. Ye can always scare a Hoon—that's ma theery, sir-r."

Craig had no further opportunity for discussing the matter, for the next morning he was "concussed" in midair and retained sufficient sense to bring his machine to the ground. Unfortunately the ground was in the temporary occupation of the German.

So Craig went philosophically into bondage.

He was taken to German Headquarters and handed over to von Zeiglemann's wing "for transport."

"This is Mr. von Mahl," introduced Zeiglemann gravely (they were going in to lunch); "you have heard of him."

Craig raised his eyebrows, for the spirit of mischief was on him.

"Von Mahl," he said with well-assumed incredulity; "why, I thought—oh, by the way, is to-day the sixteenth?"

"To-morrow is the sixteenth," snarled von Mahl. "What happens to-morrow, Herr Englishman?"

"I beg your pardon," said Craig politely; "I'm afraid I can not tell you—it would not be fair to Tam."

And von Mahl went out in a sweat of fear.

From somewhere overhead came a sound like a snarl of a buzz-saw as it bites into hard wood. Tam, who was walking along a deserted by-road, his hands in his breeches pockets, his forage cap at the back of his head, looked up and shaded his eyes. Something as big as a house-fly, and black as that, was moving with painful slowness across the skies.

Now, there is only one machine that makes a noise like a buzz-saw going about its lawful business, and that is a British battle-plane, and that this was such a machine, Tam knew.

Why it should be flying at that height and in a direction opposite to that in which the battle-line lay, was a mystery.

Usually a machine begins to drop as it reaches our lines, even though its destination may be far beyond the aerodromes immediately behind the line—even, as in this case, when it was heading straight for the sea and the English coast. Nor was it customary for an aeroplane bound for "Blighty" to begin its voyage from some point behind the German lines. Tam stood for fully five minutes watching the leisurely speck winging westward; then he retraced his steps to the aerodrome.

He found at the entrance a little group of officers who were equally interested.

"What do you make of that bus, Tam?" asked Blackie.

"She's British," said Tam cautiously.

He reached out his hands for the glasses that Blackie was offering, and focused them on the disappearing machine. Long and silently he watched her. The sun had been behind a cloud, but now one ray caught the aeroplane for a moment and turned her into a sparkling star of light. Tam put down his glasses.

"Yon's Mr. Craig's," he said impressively.

"Craig's machine? What makes you think so?"

"Sir-r," said Tam, "I wad know her anywheer. Yon's Mr. Craig's 'bus, right enough."

Blackie turned quickly and ran to his office. He spun the handle of the telephone and gave a number.

"That you, Calais? There's a Boche flying one of our machines gone in your direction—yes, one that came down in his lines last week. A Fairlight battle-plane. She's flying at sixteen thousand feet. Warn Dover."

He hung up the telephone and turned back.

Holiday-makers at a certain British coast town were treated to the spectacle of an alarm.

They gathered on the sands and on the front and watched a dozen English machines trekking upward in wide circles until they also were hovering specks in the sky. They saw them wheel suddenly and pass out to sea and then those who possessed strong glasses noted a new speck coming from the east and presently thirteen machines were mixed up and confused, like the spots that come before the eyes of some one afflicted with a liver.

From this pickle of dots one slowly descended and the trained observers standing at a point of vantage whooped for joy, for that which seemed a slow descent was, in reality, moving twice as fast as the swiftest express train and, moreover, they knew by certain signs that it was falling in flames.

A gray destroyer, its three stacks belching black smoke, cut through the sea and circled about the dÉbris of the burning machine. A little boat danced through the waves and a young man was hauled from the wreckage uttering strange and bitter words of hate.

They took him down to the ward-room of the destroyer and propped him in the commander's armchair. A businesslike doctor dabbed two ugly cuts in his head with iodine and deftly encircled his brow with a bandage. A navigating lieutenant passed him a whisky-and-soda.

"If you speak English, my gentle lad," said the commander, "honor us with your rank, title, and official number."

"Von Mahl," snapped the young man, "Royal Prussian Lieutenant of the Guard."

"You take our breath away," said the commander. "Will you explain why you were flying a British machine carrying the Allied marks?"

"I shall explain nothing," boomed the youth.

He was not pleasant to look upon, for his head was closely shaven and his forehead receded. Not to be outdone in modesty, his chin was also of a retiring character.

"Before I hand you over to the wild men of the Royal Naval Air Service, who, I understand, eat little things like you on toast, would you like to make any statement which will save you from the ignominious end which awaits all enterprising young heroes who come camouflaging as enterprising young Britons?"

Von Mahl hesitated.

"I came—because I saw the machine—it had fallen in our lines—it was an impulse."

He slipped his hand into his closely buttoned tunic and withdrew a thick wad of canvas-backed paper which, unfolded, revealed itself as a staff map of England.

This he spread on the ward-room table and the commander observed that at certain places little red circles had been drawn.

"Uppingleigh, Colnburn, Exchester," said the destroyer captain; "but these aren't places of military importance—they are German internment camps."

"Exactly!" said von Mahl; "that is where I go."

In this he spoke the truth, for to one of these he went.