"He wanted to go to the moon in my place," answered the former prisoner of the deserted house. "But why?" insisted Jack. "Because, I think, he's crazy, and he didn't really know what he did want. But he certainly had me well concealed," spoke Mark. "I'm free now, however, and as soon as I get some decent clothes on I'll go with you to the moon. I wouldn't want the moon people to see me dressed this way." "How did it happen?" asked Jack. "Tell us all about it. My! but I certainly have been puzzled since you--or rather since the person we thought was you--came back last night all bunged up. Give us the story." "I will; give me a chance. I guess that villain is gone for good." Andy Sudds came out with his gun, and insisted on taking a look down the road and around the premises. The man was nowhere in sight. "Now we're in for another delay," remarked Jack ruefully, as he gazed at the smashed window. "It seems as if we'd never get started for the moon." "Oh, yes, we will," declared Professor Henderson. "We have some extra heavy plate glass in the shop, and we can soon put in another observation window." "Let's get right to work then," proposed Jack. "That man may come back. Did you learn who he was, Mark?" "No, he wouldn't tell his name, and he said he was doing this to get revenge on us for some fancied wrong. I can't imagine who he is. But let's work and talk at the same time. I'll tell you all that happened to me," which he did briefly. Mark soon got rid of the tramp clothes, and donned an extra suit which had been packed in his trunk in the projectile. Then he helped replace the broken window, which, in spite of their haste, took nearly all the rest of the day to put in place. "Shall we wait and start to-morrow?" asked Jack, when four o'clock came. "It will soon be dark." "Darkness will make no difference to us," announced Professor Roumann. "Our Cardite motor will soon take us out of the shadow of the earth, and we will be in perpetual sunshine until we reach the moon. As we are all ready, we might as well start now." They all agreed with this, and, after a final inspection of the projectile, the travellers entered it, and Jack was once more about to seal the big door. Before he could do so there came riding into the yard, on his motorcycle, which he had claimed that afternoon, Dick Johnson. "Wait a minute," he cried. "I've got a letter for you. It's from that man!" "What--another thing to delay us?" cried Jack, but he called to Professor Roumann not to start the motor, and ran to take from Dick the letter which the lad held out. "That same man who gave me the one for Mark gave me this, and he paid me a half a dollar to bring it here," said the boy. "All right," answered Jack impatiently. He looked at the note. It was addressed to the "Moon Travellers," and, considering that he was one, the youth tore open the envelope. In the dim light of the fading day he read the bold handwriting.