AN IMPORTANT DISCOVERY
That night as he tramped the deck on his silent watch, Johnny found his
mind crowded with disturbing thoughts of the significant message the
green arrow had flashed over the sea.
"_We will strike_--" his mind went over the words again and again, "_at
the earliest possible moment!_" Where would they strike? And who was to
receive the blow? His shipmates on the _Sea Nymph_? Old Kennedy and his
daughter? Or someone he never had seen?
"I may never know," he told himself. "Spies strike in the dark."
Johnny had read that during the World War, spies had swum to the
propellers of outgoing ships laden with men and supplies. Hours later,
with the ship far out at sea, a bomb had exploded, blowing away the
propeller and leaving the ship helpless. He knew, too, that spies had
placed incendiary bombs in the holds of ships, and dumped quantities of
acid in the very bottom of a vessel, to eat its way through the steel.
"Yes," he thought, "and even now--in times of supposed peace--they are
boring in!"
* * * * * * * *
The _Sea Nymph_ left the river and put out to sea while Johnny slept.
When he awoke in mid-afternoon, they were anchored in their old position.
"How would you like to make a solo journey in the steel ball?" Dave asked
when he came on deck.
"Go--go down alone?" Johnny asked, feeling a bit strange. "That--oh,
that's O.K., I guess."
"I was down this morning," said Dave, "and my eyes are tired. There are
some pictures I'd like to have. Conditions below are all right, and
there's an off-shore breeze. We've two lines out to windward, which
should hold her steady.
"What the professor would like," he went on in a businesslike tone, "is
to have you go down, slowly, along that submerged cliff, stopping every
ten feet to take a photo floodlight picture. That will give us a
continued story of plant and animal life, down to perhaps two thousand
feet."
"Al--all right," Johnny agreed. "I can do that." But for the life of him
he could not still his heart's wild beating. He seemed to be hearing a
voice say:
"_We will strike--at the earliest possible moment!_"
He forced his lips to repeat: "Two thousand feet, you say?"
"About that. Better get ready at once. The wind may pick up."
"Yes, it may stri--pick up," Johnny agreed a little absently.
Twenty minutes later, inside the steel ball and busy taking pictures of
the wall as he stopped each ten feet, he had all but banished thoughts of
the green arrow from his mind.
* * * * * * * *
But someone else really was seeing green arrows--and plenty of them. That
was the granddaughter of old Mr. Kennedy--the man who for twenty years
had defied encroachments of foreign interests in this happy little
republic. For Mildred had gone on a hunting expedition all her own. She
was hunting spies. She had started once more over the green arrow trail
and, strangely enough, almost instantly had discovered the secret of its
markings.
During their months together she and her grandfather had spent hours on
end, tramping the jungle, and he had taught her to know all the usual
signs. The trail of some great snake in the sand--the uprooted earth,
where little wild pigs had been--the marks of a monkey's claws on the
green sprouts of a tree--all had a meaning for her.
Knowing these usual signs, she had looked for unusual ones--and had found
them. On reaching the spot where they had lost the trail on two other
occasions, she noted that the next to the last arrow was low down, while
the _last_, was some ten feet higher. So--to reach this last marking
place--someone had been obliged to climb! In doing this, bits of bark had
been broken off, leaving fresh, light-brown spots on the tree trunks.
"Now I shall look for broken bark--not arrows," she told herself.
She had not gone forward a hundred paces on the right hand fork of the
trail, when she let out a cry of surprise and joy. Not only had she
discovered broken bark, but up, perhaps thirty feet on a tree, she saw a
green arrow.
"One, two, three," she whispered. "Perhaps that's the way it goes. One
arrow down low, one a little higher, and a third, well up on the trunk!"
She discovered at once that this was just the way the markings ran. So
immediately she took up the trail again.
The distance from the shore of the island to the summit of the tallest
hill, was considerable. The trail, such as it was, made only by natives
and wild animals, wound round and round--up and up.
The girl followed this trail for more than an hour. Then she sat down on
a fallen mahogany tree to think. She was far from all her friends. Should
she go farther? She, too, recalled the last message of the green arrow of
light--about "striking"!
"Perhaps I can stop them," she whispered stoutly, as she rose to her
feet. "At least I can try!"
Though her knees trembled, she did not falter, but marched straight on.
For was she not the granddaughter of old Kennedy--hero of a hundred
battles?