At half-past four on the following morning, Kiddie stood alone on the trail with his saddled pony, waiting in the darkness outside the depot of the Express in Fort Laramie, and listening for the thumping sound of hoofs which should tell him that the westward bound mail was approaching.

He was earlier than it was necessary he should be, but he was aware from long past experience that when there was an especially important dispatch among the mails, the riders taking up their successive relays tried to gain a few minutes on their time.

And this was what now happened, for he had been waiting less than a quarter of an hour when he heard the expected sound from afar. Shortly afterwards the incoming rider dismounted at his side, breathing heavily after a ride of two hundred and forty miles.

“You’ve saved seventeen minutes on schedule time, pardner,” Kiddie told him. “Guess I shall improve on that, if my ponies are all up to the mark an’ ready at their stations.”

He seized the two satchels, transferred them to his own saddle, mounted, and with a wave of the hand started off to the westward.

Not a moment had been wasted in making the change, and his trained pony broke at once into a full gallop which would be continued while the trail was level until the next station was reached, some thirty miles away, where a fresh pony would be awaiting him.

His first relay station was at Hot Springs, and it took him less than a minute to change mounts. He rode eight different ponies on this trip, and each of them satisfied him. Their pace depended upon the nature of the ground.

Where the trail was good, as across Laramie Plain, and could be taken at the gallop, the speed was something like twenty-five miles an hour, but where the way was rugged, as among the Porcupine Mountains, fifteen, or even ten miles in an hour was considered good going.

When Kiddie reached the station at Sweetwater Bridge he had gained by six minutes. Gideon Birkenshaw had come down from the homestead to greet him, and the fresh pony was held by young Rube Carter. Kiddie’s Highland deerhound, Sheila, was also on the trail. As he dismounted, she raised herself on her hind feet and put her paws on his shoulders to lick his chin.

“Down, Sheila, down!” commanded Kiddie, drawing away from her. “I’m on duty. I’ve not come home to you.”

Sheila walked majestically apart from him.

“Amazin’ wise, that animal is,” said Gideon, taking the bridle of the tired pony, and watching Kiddie leap to the saddle of the fresh one. “Built same’s a racehorse, she is. Them long legs of hers, they’d cover a heap o’ ground, eh? What kinder work did she do in her own country, Kiddie? Huntin’?”

“Yes, deer hunting,” Kiddie answered. “She could race any stag-outdistance any horse. Has a pedigree as long’s your arm, Gid. She’s quite an aristocrat.”

“Splendidest dog I ever see in my life,” commented Rube, patting the hound’s shaggy head. He seized her collar and held her in a firm grip while Kiddie started. She strained against him as her master went farther and farther away.

Rider and pony were quickly out of sight in a fold of the trail, but again they appeared on the farther rise. Sheila pulled harder now, but Rube dug his heels in the ground, and dragged her back.

“No, you ain’t goin’ ter foller him,” he protested.

But with a sudden strong wrench the hound broke away, and bounded off along the trail, sending Rube flying backward into the bushes. Rube scrambled to his feet.

“Look! look, Boss!” he cried, excitedly. “Gee! did y’ever see a critter run like that? My! jus’ look! Kiddie may well say she c’d outdistance any hoss. D’you reckon a railroad train c’d go faster’n that, Gideon!”

“Dunno,” said Gideon, watching the animal racing at full stretch through a cloud of dust. “I ain’t just certain ’bout that railroad train; but I sure never seen a critter go along quicker’n that hound’s goin’ now. Why, she’ll overtake Kiddie inside of half an hour, for all his long start of her!”

Kiddie, indeed, had not gone half a dozen miles before the deerhound was galloping at his pony’s heels. The pony’s ears were twitching nervously, and there was a change in the measure of its headlong stride. Kiddie felt instinctively that he was being closely followed, yet there were no hungry wolves about at this time of year.

An impatient yelping bark reached him. He glanced round over his shoulder. The dog soon came level with him.

“Go back-back, Sheila!” he called.

But Sheila only slackened her pace, and dropped behind, where he could neither see nor hear her.

At a bend in the trail, where it entered a deep gully, overshadowed by trees, Kiddie looked round to assure himself that the hound had obeyed him. To his surprise he saw her still following him closely. He drew rein, dropping from a swift gallop to an easy canter. Still Sheila was close behind. Kiddie began to scold her, but, as this had no effect, he pulled up to a halt, and dismounted.

“Now, do as you’re told, Sheila,” he said, half gravely, half coaxingly. “Go back home, you’re not to come with me. I’m going too far. Go home, now; there’s a good girl.”

The hound seemed to understand, for she turned away a few steps and then looked at him pleadingly, standing with her jaws open, and her long dripping tongue working like a piston over her white fangs.

Suddenly she lifted her head, and looked sharply into the shadow of the trees. Her ears were raised as if she had heard some strange, suspicious sound.

Kiddie, preparing to re-mount, listened also. He heard the breaking of a twig far in among the thickly-growing trees. At the same instant something like the buzz-z of a mosquito passed by his ear. An arrow flashed across the trail between him and the dog, striking against a stout tree trunk on the farther side. Then a second arrow, aimed higher, rattled among the upper branches.

Now, Kiddie had his mail bags to think of. He had already lost several precious moments dealing with the hound, and he could not afford to waste time in trying to discover what possible enemy was lurking in the woods with the evident purpose of taking his life.

Drawing his revolver, he fired two shots in the direction from which the arrows had come. Then he turned to Sheila.

“Seek him, Sheila-seek him! After him-quick!” he ordered, pointing out the way; and as the deerhound plunged into the woodland he snatched up the nearer arrow, ran to his pony, and, re-mounting, renewed his broken journey.

At Three Crossings, which was his next relay station, he showed the arrow to the man who met him with the fresh pony.

“Say, Hoskin, how’s that?” he questioned. “Some skunk hidin’ in the timber this side of Medicine Creek, figured ter do me in with it. Poisoned, ain’t it?”

Hoskin took the weapon and critically examined its barbed point.

“Yep,” he nodded meaningly, handing it back. “It’s sure poisoned. A scratch with it would kill you right away. Got any partic’lar enemy among them Injuns hangin’ out along your way? What about the lot as was at Birkenshaw’s t’other morning? You was thar, I hear. What about Broken Feather?”

“Broken Feather could hardly know that I’m takin’ this trip with the Pony Express,” Kiddie demurred.

“Um!” Hoskin shook his head. “I ain’t so sure ’bout that, Kiddie,” he said. “He has spies planted all along the trail. He knows ’most everything. You’d best be keerful.”

Late on that same day. Rube Carter was crossing the trail, carrying a load of material for Kiddie’s building operations, when he saw Sheila limping towards him over the bridge. He dropped his load, strode up to her, and was putting his arms about her neck in welcome when he noticed that there was blood on her chin and throat. He searched for an open wound, but found none.

“Looks as if you’d bin gettin’ back to yer old business of huntin’ stags,” he said. “Wait, though,” he added, seeing a nasty tear in the skin over her shoulder. “Stags don’t carry no knives along of ’em, an’ if that ain’t a knife stab on your shoulder, then I sure ain’t fit t’ be called a scout.”

Rube was very much perplexed concerning Sheila’s condition. It appeared to him that, after all, she had not overtaken her master; that notwithstanding Kiddie’s confidence in her running powers, she had proved that a Highland deerhound was not the equal in speed of a well-trained prairie pony.

Rube blamed himself for having allowed her to break away from him. He was glad, however, that she was not lost, and that her injury was not serious. But where had she been? What had she been doing?

He at once began to exercise his scoutcraft in the endeavour to puzzle out the mystery.

The blood marks on her chin and throat might very well be accounted for on the supposition that, instead of following her master, she had gone aside from the trail to give chase to some large animal-a mountain goat or a big-horn antelope, and that she had attacked and perhaps killed it, as she had been trained to do when out deer-stalking in her native Highlands of Scotland.

She might very easily have been wounded in the encounter by a backward prod of an antelope’s sharp horn; even as she might have got the stains about her mouth in licking the bleeding wound.

But, unfortunately for this simple theory, the wound in the hound’s shoulder was not of a kind to suggest the stab of a goat’s horn or of an antelope’s sharp-pointed antler. It was clearly and unmistakably the cut of a knife; not round, but thin and straight, and it was too far forward and too high over her shoulder for her to turn her head and get at it with her tongue.

Moreover, some of the bristles that had been cut by the knife remained there loose among the congealing blood, showing that it had not been licked. Rube’s obvious conclusion was that it was not an animal, but a man she had attacked; that she had bitten him severely, and that he had used his knife in defending himself. But who that man might be, or why the hound should attack him, Rube could not even conjecture.

It was a dark night, and Rube was sound asleep in his bunk, when Kiddie changed ponies at Sweetwater Bridge on his eastward-bound trip; but Kiddie made time to ask Abe Harum if Sheila had returned.

Abe told him that she was then in her kennel, but added nothing about her condition. On the following day, however, when he returned home for a spell of rest, it was Rube who met him on the trail.

“Seems Abe told you as the hound had come back,” began Rube. “It was my fault she followed you. I couldn’t hardly help lettin’ her loose. Thar was no holdin’ her in. She got up t’ you, then? How long was she gettin’ abreast o’ you? I guess you hadn’t gotten far, eh? Gee! how she did cover the ground!”

“Why,” Kiddie answered, “she was alongside o’ me inside of six miles from here. Good going, wasn’t it?”

“Sure,” agreed Rube. “But she didn’t come back so quick, Kiddie, nothin’ like it. Did yer know she’d a cut on her shoulder?”

“Eh-a cut?” Kiddie started in vexed surprise. “Is it bad?”

“Oh, no,” Rube assured him, “makes her limp some. But I’ve doctored th’ wound, an’ it’s gettin’ along all right. Come an’ have a squint at it.”

He brought the dog out, giving no expression to his own theory. Kiddie examined the wound.

“Cut of a knife,” he decided immediately.

“Thar was blood on her mouth,” said Rube. “I washed it. ’Twasn’t her own blood.”

“Then they sure got to close grips,” concluded Kiddie, “and I guess he got as much as he gave. She’d make for his throat, but I’m figurín’ that he’d put up an arm to protect himself. His left arm, most like, as he’d use his right for the knife. We gotter keep our eyes open for a man with a lame left arm, Rube.”

“Didn’t yer see him, Kiddie?” Rube questioned.

“No.”

“Then how d’you know anythin’ about it? How d’you know it was a man as done it? How d’you know she didn’t kill him outright, same’s she’d kill a stag? An’ why did she go for him, anyway?”

“She went for him because I sent her into the forest after him,” Kiddie explained. “The scoundrel shot a poisoned arrow at me. And, having myself no time to spare, I left the business to the dog, see?”

“An arrow!” exclaimed Rube, “a poisoned arrow! Well, ’twas sure a Injun done it. Any one else ’ud have used a gun.”

“Might have been a white man, for all that,” resumed Kiddie. “An arrow’s a silent weapon, and if it’s poisoned, as this one certainly was, then a mere scratch would be fatal; whereas the victim might recover from a bullet wound. Whoever it was, however, Sheila must sure have left the mark of her fangs on him.”

“How d’you know she didn’t kill him?” Rube persisted. “How d’you know he ain’t lyin’ there dead, right now?”

“Because,” Kiddie rejoined, “on my return trip-knowing exactly where the thing happened-I went into the forest and searched. I found spots of blood. I found signs of the struggle; that was all. There wasn’t any dead body lyin’ around.”

“P’raps th’ other Redskins carried his body away,” conjectured Rube.

“But he was alone,” pursued Kiddie. “I’m plumb sure there was nobody with him.”

“See the marks of his moccasins?”

“No. He wore nailed boots, which left scratches on the root of a cotton wood tree.”

“Boots, eh? A Injun would have wore moccasins that wouldn’t leave no scratch, even on the soft bark of a tree root. Y’see, a white man might wear moccasins, same’s I do; but I never knew a Redskin shove his hoofs inter hob-nailed boots. Wait, Kiddie, wait! I’ve gotten a idea.”

“Let’s hear it, then, Rube. I’m glad to find that you’re exercising your powers of reasoning. What’s your idea?”

“This,” declared Rube, with a knowing headshake. “I was figurín’ that the low-down scoundrel as fired that poisoned arrow might be-well, might be Nick Undrell. I never told you before, Kiddie, but that day when your outfit was attacked by the Injuns, I heard one of Nick’s chums say ter him-time you was ridin’ alone in advance of the wagons-that now was the chance if Nick had a mind ter put a bullet inter you an’ vamoose wi’ the boodle.”

“Yes,” smiled Kiddie, “and your idea is that because one of his chums said such a thing as that, Nick went miles and miles out of his way to hide himself in Medicine Creek Forest and try to do the trick by putting a poisoned arrow into me, eh? And what d’you reckon might have been his motive?”

“Dunno,” answered Rube. “Never thought of that.”

“Because,” pursued Kiddie, “if it was robbery, an experienced frontiersman like Nick Undrell wouldn’t calculate on finding much boodle on a Pony Express rider. He’d find it a heap more profitable to do the robbery right here where all my valuables are. Besides, Nick is too slick a hand with the pistol to have any truck with an Injun’s bow and arrows. No, Rube, my boy, your idea isn’t worth a whole lot, come to analyze it. Even if I suspected Nick Undrell of shooting that arrow, the fact remains that when I started on that ride I left him in Fort Laramie, that he had no relays of ponies, as I had, waiting ready along the trail, and that he couldn’t anyhow have got to Medicine Creek in front of me. It wasn’t humanly possible. Any other solution ter suggest, Rube?”

Rube shook his head decisively.

“No,” he answered. “I’m just more puzzled than ever. Can’t straighten it out nohow. Can’t think who it could be, or why he did it. Thar’s only one thing t’ be said, Kiddie, an’ that’s this: the man as tried ter take your life was either a Injun wearin’ white man’s boots, or else a white man usin’ a Injun’s bow an’ arrow. Beyond that, I’m makin’ up my mind ter look out fer a individual-red or white-goin’ around with his left arm in a sling.”

“Don’t hold too tight t’ th’ idea that it was in the arm he was bitten-” Kiddie cautioned. “Sheila might have seized on any other part of his anatomy. My own notion is that the hound herself will spot him sooner’n you or I could do.”

“Thar’s a lot in that notion,” Rube acknowledged. “Guess I’ll keep my eye on the hound all the time. An’ when I sees her bristles rise an’ her teeth showin’ an’ hears a growl rumblin’ up from her throat, I shall sure know that the skunk ain’t a far way off.”