Chapter X: The Invisible Footprint

“I scream?” The girl in the patched knickers sitting before the roaring fire 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 mortal agony, could scream in that manner. What did it mean? Who—?

His thoughts were broken off by a sudden burst of laughter. It was the mystery girl.

“That—that,” she stammered, with an effort at self control. “It was not I who screamed, but a loon, a silly old loon! Have you never heard a loon scream in the night?”

“Never.”

“Then you are to be forgiven. When a loon goes about the business of screaming in earnest, he can put a drowning woman to shame. We who have heard them often become so accustomed to them that we scarcely hear them at all.”

Red stared first at the girl, then at the fire. He was wondering in a vague sort of way just how much he had missed by living all his life within the confines of a city. He was to wonder this many times before this business of being kidnaped and carried to a deserted island was over.

“I wonder what that old loon is doing here?” the girl mused. “All his pals must have gone south by now. The gulls stay all winter. Some kinds of ducks, too, and the jays and the chickadees. It can’t be very lonely here even in winter. Wouldn’t it be thrilling if we had to stay here on and on?”

Red stared harder at the fire as he tried in vain to think what that would be like.

“You seem to know a lot about this island,” he blurted out quite suddenly. “How does it happen that kidnapers bring you to a place where you have been before? Seems a trifle mixed.”

“I’ve wondered about that.” Her big blue eyes were round and frank. “I think I’ve got it figured out. Do you believe in God?”

“Why, yes, I—I do. I’ve prayed about football sometimes; asked the One who gave me my body to help me keep it clean and fit; asked Him, too, to give me a clear brain and a sharp eye for every play.”

“Oh,” she breathed, dropping a hand gently on his arm, “I’m glad! Because I—I believe in God. I hope He outwits evil men. And I—I’ve sort of felt that He saw that those men were going to carry us off, you and me, so He sort of winked, don’t you know, like the man in the moon seems to do, and He said: ‘I’ll have those kidnapers take that boy and girl to the island where the girl has spent her summers as long as she can remember.’ And so, 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 shower of sparks had subsided, he turned to her eagerly.

“What place is this? Tell me about it, all you can. We—we may be parted at 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, in the end, to see that justice is done.”

At the thought of the kidnapers he strode to the door and opened it a crack.

“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 remained closed so long that Red thought her asleep. But again they opened. “You are right, they will not find us in the snow. You should know about this place. 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 escape from 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 of respect for her desire he did his best to show great astonishment. The truth was that the part of social science that deals with the world we live in had interested him very little. He was all for chemistry, physics, mathematics. He had no more notion where Isle Royale was than the Little Diomede Island, or King William’s Land. He had never heard of it. “But she evidently thinks it a great place,” he told himself, “so great it shall be.”

“Tell me more about it,” he demanded at last. He was truly interested. If he was to escape from this island, wild and uninhabited as it appeared to be, he must at least know his way about.

* * * * * * * *

In the meantime, Tom Howe, in his box-like laboratory, had revealed to Johnny Thompson’s astonished eyes a bit of scientific crime detection that for sheer cunning would have put any ancient astrologer or alchemist to shame.

Having spread the bed sheet taken from Red Rodger’s berth out on a small table, he had switched on a 200-watt lamp and had proceeded to examine it inch 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 very heavy man. He left a deep dent in the mattress and bedding. It’s hard to step 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 on the smooth top of the table. “It would be about there.”

He turned off the powerful light. At once the room was plunged in utter darkness.

Then, while Johnny waited as breathless as a child at his first picture show, 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 quite clearly 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. You could count those nails. And a heel of some hard, prepared stuff with the maker’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 marks the shoe. It’s not like any other shoe in the world. Find that shoe, find the 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 a moment ago.”

“Nor is it now.” Tom Howe chuckled. The violet light faded; the brilliant white light flashed on. The footprint was gone.

“Magic!” Johnny murmured. “Some form of magic. You can’t convict a man with magic.”

“Not magic, but science!” Howe’s tone was impressive. “Crooks are learning to use science as an aid in committing crimes. We must use science to detect crimes.”

Once again the white light was gone; the violet light returned and with it that mysterious vanishing footprint.

“You see,” Howe explained, “when that fellow entered the car to assist in carrying the famous football star away, he had been walking over a surface that contained some chemical solution. If he had passed over damp coffee 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 a mark invisible in white light, but quite clearly outlined when subjected to the rays of an ultra-violet lamp.

“This lamp,” he went on, “has detected the secret writing of many a spy and jailbird. A spy, wishing to forward a secret report, dips his pen into a liquid made by soaking a few quinine pills in water. This writing will not show in white light until it has been treated. He writes some commonplace letter over this message and sends it forth. Our Secret service men seize it, put it under the ultra-violet lamp, and there it is; you can read every word. The moment the lamp is snapped off the message is gone.

“A criminal may dip the corner of his jacket in coffee, return to his cell, wring out the coffee and write with the coffee a secret message to some one who plots his deliverance. He, too, may be caught by this ultra-violet lamp.

“So now,” he concluded, “we have only to find the man who wears this shoe. Very simple in a city of three million.” He smiled a slow smile. “All the same, it’s a step.”

“An invisible step,” Johnny chuckled.