"Remain quietly where you are, then," Jimmie said, with a significant flourish at the gun which he had no intention of using, except in a case of the direst necessity.
"Go!" shouted the other.
Jimmie did not know what to do. While he had learned a good deal about the submarine, he was by no means an expert in the handling of her. His experience with the air machines had been very slight, as the boys had made little use of them.
"It's getting close in here already!" cried the captive in alarm. "Why don't you do something?"
"What is there for me to do?" asked the boy.
"Release me and I'll fix it," suggested the other.
Before Jimmie could explain the foolishness of this proposition, he heard a pounding at the outer door of the water chamber. He bounded through the open doorway and looked out.
There was a helmeted face against the pane. The boy was motioning for the door to be opened.
"Now," mused Jimmie, "I wonder how he got up there? The lifting lines haven't moved. Why didn't he let me know he was coming up?"
"Hurry!" called the captive.