it was not far to the edge of the lake, and, as you will remember, there was abundant undergrowth, but the fleeing tramps had left a trail of broken and twisted branches which it would have been easy to follow, even with greater distance and more uncertainty of direction. mike kept a few paces in the lead, and soon caught the shimmer of water, but when he glanced around saw nothing of his craft. he stood perplexed when dr. spellman stepped beside him.

“where’s the canoe?” asked the man.

“that’s what meself would like to know.”

“is this the spot where you stepped ashore?”

mike moved farther until his shoes touched the water. he recognized the projecting limb of a beech which had attracted his notice when he came ashore.

“there’s no mistake about the same. now, docther, that boat can’t hev a habit of sneakin’ off whin ye’re not watching—what’s the matter?”

his companion touched his arm and pointed over the water.

“there’s the answer to your question.”

“it beats me, as the drum said to the drum stick.”

some two hundred yards out on gosling lake was the canoe heading toward the western end of the sheet of water. in it were seated biggs and hutt, the two rascally tramps, their appearance suggesting that they were owners of the graceful craft in which they were making a pleasure excursion. their backs were toward the two on shore, but hutt who sat near the stern turned his head. observing the indignant couple, he waved his hand in salutation and grinned so broadly that the gleam of his yellow teeth showed.

neither mike nor the doctor spoke for a moment or two. then the youth solemnly extended his hand.

“docther, would ye mind shaking?”

“certainly not, but what is the idea, mike?”

“’cause i can’t think of anything ilse to do, as the p’liceman said whin he prosaaded to break his club over the head of ivery one in sight.”

“were there ever two such pests? the next time i get a chance i won’t kill them, but i’ll give each something he’ll remember.”

“where’s your boat?”

“at the foot of the path leading to the house; the distance is so short that i did not use it, but strolled to this point.”

“let’s jump into the same and make fur these spalpeens.”

the physician was so angry that he did not hesitate. they hurried through the wood to the spot where the other craft lay as it had been left by its owner. it has been shown that from this spot the house was not visible and therefore the wife and daughter knew nothing of what was afoot, which perhaps was best. the doctor, being the most skilful with the paddle, took up the implement, and headed after the other craft, which was making good progress toward the farther end of the lake.

each of our friends had asked himself the question as to what biggs and hutt meant by their act and what they were likely to do. it could not be seen that the vagrants had anything to gain, for they must soon abandon the canoe and continue their flight on foot. they knew the medical man carried a deadly weapon, and did not seem backward in using it, because of which they certainly could not desire another meeting with him.

moreover, a third canoe was involved. it seemed to have disappeared for the time, but must be somewhere near the western end of the lake, which being the case, the tramps were likely to find themselves between two fires, though it was not to be supposed that they had any cause to fear the unarmed boy scouts in the invisible boat.

the flight and pursuit had lasted only a few minutes when an unpleasant truth impressed itself upon mike and the doctor:—buzby biggs, who swung the other paddle, did it so deftly that his boat steadily drew away from the pursuer despite the utmost efforts of dr. spellman. in a straightaway race the tramps were sure to win, but the course had bounds, and in the end they must be pocketed, a fact so apparent that they themselves saw it from the first. they had the choice of keeping directly on until they reached the western margin so far in advance of their pursuers that they need give them no thought, or they could take the shorter course to the northern shore, opposite the bungalow. it looked as if they had decided upon the former plan, which would indicate that they knew or suspected nothing of the third canoe, nestling somewhere under the overhanging limbs along shore.

such undoubtedly would have been the action of the tramps, had not it changed so abruptly and inexplicably that the astounded doctor ceased paddling and stared without speaking a word.

since our friends sat with their faces toward the backs of biggs and hutt, they saw their every movement no matter how slight. hutt was idle, with a grimy hand resting on either gunwale of the canoe. now and then he glanced back and when he saw the pursuers steadily falling behind, had the impudence to reach out one hand and beckon them to move faster. the other, knowing he could not be overtaken, showed little interest in those who were striving to come up with him. something far in advance seemed to hold his attention.

such was the situation, and the forward boat was within a furlong of the western shore when biggs suddenly held his paddle suspended as if he had caught sight of some object that startled him. the next moment he flung aside the implement, uttered a cry of terror and dived overboard. hutt was not five seconds behind him. both stayed so long under water that our friends suspected they were drowned, but the frowsy heads, one without a hat, bobbed up at some distance from the boat, and they were seen swimming furiously toward the northern bank, which was not far off.

they had not taken a dozen strokes when they dived again and went as far under the surface as before. thus diving, swimming and working desperately, they quickly reached land, scrambled out, plunged in among the trees and vanished as if death himself were nipping at their heels. never was greater panic shown.

doctor spellman sat mute and motionless until the tramps had disappeared. then he turned his head:

“what do you make of that, mike?”

the occasion was one of the rare ones when the irish youth had nothing to say. he sighed and shook his head; he couldn’t do justice to the theme.

“something scared both of them out of their wits. it couldn’t have been on the shore ahead, for that’s too far off, nor on their right, for they tried with might and main to reach land there.”

“could it have been at the rear?” ventured mike.

“that is toward us. we couldn’t have caused them such alarm.”

“mr. hutt may have looked around and catched the frown on me brow; i’m towld i have a tumble exprission when i’m mad.”

“it must be true to cause them thus to leap into clear spring water, knowing it meant the coldest kind of a bath. no, mike,” added the doctor gravely, “they saw something in the water that threw them into fits. what could it be?”

this was the only theory possible and yet it simply deepened the mystery. what could there be in the clear cool waters of gosling lake, besides the different species of ordinary fishes that are taken with hook and line? to mike and the doctor the puzzle was more inexplainable than before.

one conclusion, however, was warranted by what had occurred: if the tramps had seen something which terrified them beyond imagination, what was to prevent the man and youth from gaining a sight of the same frightful object whatever it might be?

now, while it cannot be denied that dr. spellman and mike murphy were more than ordinarily brave, yet they felt a shrinking in stealing up to the spot where the tramps had dived from the other canoe. it was their ignorance of the character of the peril which affected them more than any tangible danger could have done.

the doctor dipped his paddle in the water and gently swayed it. the boat moved slowly toward the other canoe, drifting like an eggshell over the placid surface. in leaping overboard, buzby biggs had flung the paddle from him and it was seen floating a couple of rods distant from the boat. very slowly the doctor advanced until mike leaned over and lifted the implement into their craft. then the man sheered his boat beside the other and mike, tossing the paddle into it, held it steady, and sat down.

“now, docther, we can manage it, i’m thinking,” remarked the youth, looking up into the face that it seemed to him had gone a little pale.

“can you find anything to explain the fright of the tramps, mike?”

both peered into the clear water, whose depth was too great for them to see the bottom, but nothing rewarded their piercing scrutiny. and right here a fact must be admitted which was not discreditable to either of them. the breath of air that sighed over the lake had swept the empty canoe fully a hundred feet from whence it was at the moment buzby biggs dived overboard. it followed, therefore, that when mike and the doctor peered into the pellucid depths, it was not at the spot where the tramps had descried something which unnerved them. moreover, each of the pursuers knew such was the case, but did not try to correct it nor did either drop a hint of his knowledge until some time afterward.

it may be added that had the doctor and his young friend paddled a little farther in the proper direction they would have solved the mystery and been overcome probably by the same panic that had driven the tramps overboard.

“well,” said the physician, “there is nothing to be gained by staying here. let’s go to my home, have supper and spend the evening. i know my wife will be glad to have you, and i suspect that stubby feels a little that way herself.”

“i hope so,” replied mike feelingly; “i may as well confess that my main purpose in going thither is to meet sunbeam, as the callers used to say regarding mesilf whin they purtended they wanted to see dad and mither.”

paddling at a leisurely rate, they soon drew the two canoes up the bank and stepped out. mike paused and looked back.

“can there be any fear of thim spalpeens poking round here while we’re not in sight?”

“it seems unlikely; since they tried that 43sort of thing they have been scared so fearfully that i think they will avoid us.”

“docther, what could it have been that made them jump out of their boat and swim and dive like two crazy persons?”

“i should give a good deal to be able to answer that question, but i have no more idea than you. let us try to content ourselves with the belief that like the cause of uncle elk’s resentment toward me, it will be made clear sooner or later.”

before leaving the landing, as it may be called, they scanned the surface of the lake. the doctor generally carried his binoculars and he traced the margin clear around from their right back again to their left. there stood the bungalow with the flag idly drooping from the staff and several of the scouts were seen lounging at the front. in no other direction was a sign of life discerned.

“i cannot discover the other canoe,” remarked dr. spellman, passing the glass to mike at his side. “if the boys had returned, the boat would be in sight by the bungalow; whoever used it, they are still absent.”

“they have landed and gone into the woods to look after birds or to trace out other kinds of trees. they will be back before the set of sun.”

“no doubt, unless,” added the doctor half in earnest, “they should receive the same shock that struck biggs and hutt.”

“in that evint, they will be home still earlier.”

“come on; i’m beginning to feel hungry.”

“and i’m wid ye there.”