“We can’t always be successful,” commented Bob. “Whew! I’m tired. I’m going to have a rest.”
He sat down on a grassy spot. Just below them was the Comet, which had been fully repaired, and was all ready for the homeward trip. Ned and Jerry walked on a little way, and then took a seat on a log, for they, too, were weary. They talked over their adventures, agreeing that, even though they had not found the radium treasure, they had had a good vacation.
Bob suddenly jumped up, and rubbed his thigh.
“What’s the matter; sit on a thorn?” asked Ned with a laugh.
“Something like that,” answered the stout lad. “Or else a bee stung me. Well, come on. It’s all over.”
They were packing up that night, ready for the trip home in the morning, when Bob complained of a burning sensation in his leg.
“Better let me look at it,” suggested the professor, who knew something of medicine. “You may have been poisoned by some insect.” But, when he had looked at a peculiar red spot on Bob’s leg he cried out:
“Boys, that’s the most wonderful thing I ever heard of! Bob has solved the riddle for us!”
“What riddle?” demanded Jerry eagerly.
“The radium riddle! That’s a blister caused by emanations from radium!” went on the professor. “Look at it, Mr. Bentwell, and see if you don’t think so!”