Together the boys pushed and shoved. But all to no purpose. Flashing their lights on the obstruction, they saw that it had fallen down in a wedged-shaped place, dove-tailing itself in so that no power short of dynamite could loosen it. The hopelessness of moving it struck them at once.
"The other end!" cried Frank. "We must try to get out the other way!"
Back they raced along the passage, slipping stumbling on the wet, rocky floor. But it only to come face to face with a solid wall of rock.
"No use trying to get through there," said Andy. "We must try to move the big rock."
"We can't," spoke Frank. "I think——" But he never finished that sentence. Instead focused his light down on the stone floor of passage in the cave. A thin stream of water trickling along it.
"Look! Look!" whispered Andy.
"Yes," answered his brother in a low voice. "The tide is rising. It's running into the cave, and we—we're trapped here, Andy. No wonder that man said it was the last time. We're trapped by the rising tide!"
CHAPTER XXI
DEATH IS NEAR
"Frank, are you there?"