“I’m not,” declared Tom, but his manager could see that he was and that he could not get his mind down to work. At last Tom himself became aware of his nervous condition, and shortly after noon, throwing his pencil down on his desk, he exclaimed: “I’m going out for a ride, Ned. Come along. It will clear the cobwebs out of our brains.” “Going in the runabout?” asked Ned. “No, in the little biplane. She’s just been tuned up and runs like a sewing machine. We’ll take a spin up in the clouds.” Ned considered for a moment, looked at a mass of papers on his desk, and answered: “No, thank you, I’d better not go. Besides, Mr. Plum just telephoned that he’d like to see me about dad’s case, and I want to run over there.” “All right,” agreed Tom. “Take all the time you want, Ned. But I don’t want to go skylarking alone. I think I’ll ’phone Mary. I haven’t had her up in the biplane for some time.” “Yes, you and Mary go for a spin,” replied Ned. “Only take care that it isn’t a tail-spin.” “The _Hummer_ doesn’t indulge in such antics,” replied Tom, with a laugh. “But first I’d better see if she’ll tune up as she did the other day. I don’t want to get Mary out in her and then have something go wrong. I’ll just run her out, Ned, and give her a warming up. Then, if everything’s all right, I’ll call Mary. You can look after things here, I suppose?” “Yes, either dad or I will. He’ll be back soon, and then I’ll take a run over to Plum’s office.” Tom owned several planes, but of the two-winged variety the one he best liked was the _Hummer_, a small but speedy craft. This machine was kept in a hanger near the flying field, and it did not take the young inventor long to have her run out that he might test the engine. “She sure sounds sweet, Mr. Swift,” remarked the mechanician who assisted him. “Yes, Dirk, she’s throbbing like a wild duck. I guess I’ll take her up for a time.” Going back to the office Tom reported to Ned that everything about the _Hummer_ was in good shape and that he would probably be gone for the remainder of the day. As there was no good landing place near the home of Mary Nestor it was necessary for her to come to Tom’s flying field, and while he was getting ready he sent one of his men for the young lady in an automobile. But first Tom called her on the telephone. “Oh, Tom!” exclaimed Mary, as soon as she found who was on the wire, “I was just going to call you up!” “You were?” “Yes, it’s awfully important! I want to see you very much!” “Well, you’ll have that pleasure directly.” “Oh, Tom, don’t joke about it! It is important.” “What’s the trouble, Mary,” the young inventor asked, seriously enough now. “I’ll tell you when I see you—soon!” Tom told the girl of the proposed trip and Mary hung up the receiver while Tom wondered at the note of anxiety in his sweetheart’s message. CHAPTER X A QUEER STORY