He made as though to rise, but Jack stayed him.
"Wait and see what happens," he said softly.
Both leaned back in their chairs and seemed to pay no further heed to the window. But without looking each became aware that the window was being raised softly, and clear across the room they could hear the breathing of a man. A foot sounded on the floor and at that moment both boys sprang to their feet and faced the intruder.
Before either could speak, the newcomer laid a finger to his lips in a sign for silence and came toward them.
"Quick!" he whispered, when he was close to them. "Tell me what you have learned. This may be your only chance!"
Frank and Jack stepped back in astonishment.
"Tell you what?" demanded the latter.
"What you have learned," repeated the man. "About the vanishing submarines. What has happened to them?"
Noticing the apparently puzzled looks on the faces of the two boys, the man smiled slightly and thrust a hand into his inside vest pocket.
"I see," he whispered. "You want to be sure it is all right. Here. Look!" he exhibited a small card. "My number. Thirty-two. See it?"