CHAPTER X THE INVISIBLE FOOTPRINT
"I scream?" The girl in the patched knickers sitting before the roaringfire stared at Red Rodgers. "Why should I scream?"
"I don't know." Red was puzzled. "I only know I heard you."
"But I did not scream."
It was Red's turn to start. He had heard a scream. No man, even in mortalagony, could scream in that manner. What did it mean? Who--?
His thoughts were broken off by a sudden burst of laughter. It was themystery girl.
"That--that," she stammered, with an effort at self control. "It was notI who screamed, but a loon, a silly old loon! Have you never heard a loonscream in the night?"
"Never."
"Then you are to be forgiven. When a loon goes about the business ofscreaming in earnest, he can put a drowning woman to shame. We who haveheard them often become so accustomed to them that we scarcely hear themat all."
Red stared first at the girl, then at the fire. He was wondering in avague sort of way just how much he had missed by living all his lifewithin the confines of a city. He was to wonder this many times beforethis business of being kidnaped and carried to a deserted island wasover.
"I wonder what that old loon is doing here?" the girl mused. "All hispals must have gone south by now. The gulls stay all winter. Some kindsof ducks, too, and the jays and the chickadees. It can't be very lonelyhere even in winter. Wouldn't it be thrilling if we had to stay here onand on?"
Red stared harder at the fire as he tried in vain to think what thatwould be like.
"You seem to know a lot about this island," he blurted out quitesuddenly. "How does it happen that kidnapers bring you to a place whereyou have been before? Seems a trifle mixed."
"I've wondered about that." Her big blue eyes were round and frank. "Ithink I've got it figured out. Do you believe in God?"
"Why, yes, I--I do. I've prayed about football sometimes; asked the Onewho gave me my body to help me keep it clean and fit; asked Him, too, togive me a clear brain and a sharp eye for every play."
"Oh," she breathed, dropping a hand gently on his arm, "I'm glad! BecauseI--I believe in God. I hope He outwits evil men. And I--I've sort of feltthat He saw that those men were going to carry us off, you and me, so Hesort of winked, don't you know, like the man in the moon seems to do, andHe said: 'I'll have those kidnapers take that boy and girl to the islandwhere the girl has spent her summers as long as she can remember.' Andso, don't you see? Here we are."
"That," said Red with conviction, "that's great!"
Reaching for a large spruce log, he threw it on the fire. When the showerof sparks had subsided, he turned to her eagerly.
"What place is this? Tell me about it, all you can. We--we may be partedat any moment. And I--I need to know a lot. In the end they may get us,at least one of us, and the other must be able to make his way out, inthe end, to see that justice is done."
At the thought of the kidnapers he strode to the door and opened it acrack.
"Safe enough for the present." His tension relaxed. "It's snowing,snowing hard. They'll never find us here in a snowstorm."
"You are right," she replied quietly. Her eyes closed. They remainedclosed so long that Red thought her asleep. But again they opened. "Youare right, they will not find us in the snow. You should know about thisplace. I will tell you all I can. And then--then we must rest, for long,hard hours are before us. It is difficult, perhaps impossible, to escapefrom this place in November. But we must try."
"What place is this?" the boy asked once more.
"What? You don't know our island?" The girl's eyes opened wide. "This,"her tone became impressive, "this is Isle Royale!"
"She expects me to be greatly surprised," Red said to himself. Out ofrespect for her desire he did his best to show great astonishment. Thetruth was that the part of social science that deals with the world welive in had interested him very little. He was all for chemistry,physics, mathematics. He had no more notion where Isle Royale was thanthe Little Diomede Island, or King William's Land. He had never heard ofit. "But she evidently thinks it a great place," he told himself, "sogreat it shall be."
"Tell me more about it," he demanded at last. He was truly interested. Ifhe was to escape from this island, wild and uninhabited as it appeared tobe, he must at least know his way about.
* * * * * * * *
In the meantime, Tom Howe, in his box-like laboratory, had revealed toJohnny Thompson's astonished eyes a bit of scientific crime detectionthat for sheer cunning would have put any ancient astrologer or alchemistto shame.
Having spread the bed sheet taken from Red Rodger's berth out on a smalltable, he had switched on a 200-watt lamp and had proceeded to examine itinch by inch as he slid it across the table.
"Not a mark," Johnny commented, as the examination was completed.
"I'm not so sure," Howe drawled. "A man stepped on that sheet, a veryheavy man. He left a deep dent in the mattress and bedding. It's hard tostep on anything as clean as a sheet without leaving some sort of mark.
"Let's see." He drew the sheet endwise until the very center rested onthe smooth top of the table. "It would be about there."
He turned off the powerful light. At once the room was plunged in utterdarkness.
Then, while Johnny waited as breathless as a child at his first pictureshow, a curious violet light pervaded the room.
"Look!" Tom Howe whispered, pointing to the center of the sheet.
Johnny did look, and there, to his vast astonishment, he beheld quiteclearly outlined the footprint of a man.
"The sole of a heavy shoe!" He was dumbfounded. "It was not there before!And see! There are the marks of the nails; a heavy workman's shoe. Youcould count those nails. And a heel of some hard, prepared stuff with themaker's name wrong way over."
"Yes," Howe added quietly, "and a deep, jagged cut across the sole.Slipped on some sharp stone perhaps, when the sole was wet. That marksthe shoe. It's not like any other shoe in the world. Find that shoe, findthe man who wears it, and we have made a discovery of great importance."
"But I don't understand!" Johnny was puzzled. "That mark was not there amoment ago."
"Nor is it now." Tom Howe chuckled. The violet light faded; the brilliantwhite light flashed on. The footprint was gone.
"Magic!" Johnny murmured. "Some form of magic. You can't convict a manwith magic."
"Not magic, but science!" Howe's tone was impressive. "Crooks arelearning to use science as an aid in committing crimes. We must usescience to detect crimes."
Once again the white light was gone; the violet light returned and withit that mysterious vanishing footprint.
"You see," Howe explained, "when that fellow entered the car to assist incarrying the famous football star away, he had been walking over asurface that contained some chemical solution. If he had passed over dampcoffee grounds, or through a forest where rank vegetable matter rotted,the effect would have been as you see it now. His foot would have left amark invisible in white light, but quite clearly outlined when subjectedto the rays of an ultra-violet lamp.
"This lamp," he went on, "has detected the secret writing of many a spyand jailbird. A spy, wishing to forward a secret report, dips his peninto a liquid made by soaking a few quinine pills in water. This writingwill not show in white light until it has been treated. He writes somecommonplace letter over this message and sends it forth. Our Secretservice men seize it, put it under the ultra-violet lamp, and there itis; you can read every word. The moment the lamp is snapped off themessage is gone.
"A criminal may dip the corner of his jacket in coffee, return to hiscell, wring out the coffee and write with the coffee a secret message tosome one who plots his deliverance. He, too, may be caught by thisultra-violet lamp.
"So now," he concluded, "we have only to find the man who wears thisshoe. Very simple in a city of three million." He smiled a slow smile."All the same, it's a step."
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"An invisible step," Johnny chuckled.