Publisher's Synopsis
I wonder if any of you are superstitious, or if you believe in "signs"? I, myself, do not, but as this happens to be the thirteenth book in the Motor Boys series, I just thought I'd mention it, more as a joke than anything else.You know some persons think thirteen is unlucky. I do not, and I am sure you do not, either. So I venture to hope that I have been lucky enough to write for you, in this thirteenth volume, a book you will like better than any of the preceding ones that I have been happy to pen.Certainly, Jerry, Ned and Bob, when they went after the radium treasure, on Snake Island, in the Grand Canyon of the Colorado, had a chance to believe in "signs" if they were so inclined. But when they saw the strange "ghosts" they were not a bit frightened, and, later on, they discovered the cause of them.
