“But not today,” said Johnny. “The shadows already are growing long.”
By the time they reached the beach from which the singing band had so mysteriously disappeared, the abrupt, tropical darkness had fallen. For a moment they stood looking at the dark, mysterious sea. Suddenly Mildred gripped Johnny’s arm and whispered:
“Look! The green arrow!”
True enough. Seeming but a stone’s throw from shore, the green arrow appeared to rise from the sea.
“It must be on a submarine!” Mildred whispered.
“Wait! They’re signalling.” Johnny dragged pencil and paper from his pocket and began scribbling numbers. This continued for two minutes. Then, as suddenly as it had appeared, the green arrow vanished.
“Gone!” the girl exclaimed.
“Come on,” said Johnny. “I want to see what they were saying.”
Leading the way to a dark hollow where their light could not be seen, he asked her to hold the electric torch while he deciphered the message.
“‘We will strike,’” he read aloud, “‘at the earliest possible moment!’