He broke off, startled to hear a murmur of voices from a short distance down the beach. Quick as a flash he blew out the lantern and hung it in its accustomed place on the wall nail.
“Salt! Those men are coming!” Penny whispered fearfully. “We’re trapped here!”
It was too late to slip out the door, for already the men were very close, and unmistakably, one of the voices was that of Professor Bettenridge.
The only available hiding place was a storage closet. Barely in time, Salt and Penny squeezed into it, closing the door and flattening themselves against the wall.
The door of the shack swung open to admit the professor, Webb, and Mr. Johnson.
“Dark as pitch in here,” Webb muttered. “Wait and I’ll light the lantern.”
In a moment the yellow glow illuminated the dingy little room.
“Which is my mine?” Mr. Johnson asked. “They all look alike.”
“And for all practical purposes they are exactly alike,” said the professor smoothly. “So far as my machine is concerned, it makes not a particle of difference. Webb, which is the mine that Mr. Johnson supplied?”
“Here it is,” the assistant said, tapping the one Salt and Penny had substituted. “See your initials, Mr. Johnson?”