“I’ll send him to you,” Mr. Swift offered. “What’s the matter, Tom? What are you going to have Clark do?” “Some detective work,” was the low answer. CHAPTER IV A STRANGE MESSAGE TOM SWIFT sank wearily into a chair, facing his damaged talking-picture machine. That it was very seriously damaged was plainer to the eyes of the young inventor than to those even of his father, who was one of three persons aware of what great changes the new machine was destined to bring about. But Tom rallied and from the ruins of his invention saw mentally, rising like the fabled Phoenix from its own ashes, a new and better piece of apparatus. “Maybe, after all,” mused Tom, “this will turn out better than it looked at first sight. I already have an idea for some improvements in the new machine I’m going to start—as soon as I’m able,” he added somewhat grimly. “Tom, you’d better go back to bed!” exclaimed his father anxiously. “You know Dr. Layton said——” “Oh, I’m all right!” protested the young inventor. “I’m going slow. I do feel a bit pulled out, but I don’t intend to do any work. However, I’m on the track of something, and it’s got to be followed up.” “Then you think this was deliberately done, Tom?” asked Mr. Swift as he finished sending a message to have Jim Clark sent to Tom’s private quarters. “I’m almost positive of it,” was the reply. “And I have under suspicion a certain man.” “Who?” asked Mr. Swift in a low voice, making sure no one was near the shattered door. “Greenbaum,” was the equally low answer. “Why, I thought he was one of your best workers, Tom!” exclaimed Mr. Swift in surprise. “So he is, in his own particular line. But now that I think matters over, I see that there is a chance he had something to do with this explosion. He was here in the laboratory just before it happened. He and I and Ned Newton were the only ones here, as a matter of fact. Ned has disappeared, and that’s worrying me, but I’ll come to that feature in due time. I guess Ned can look after himself, though his disappearance is certainly mysterious, coupled with everything else that’s happened. But when I stop to think about Greenbaum being here just before the explosion——” “But, Tom,” interrupted his father, “I thought you said Greenbaum went before you locked up and came home.” “Apparently he did. But he may have come back. That’s what I want Clark to do—a bit of detective work to find out if Greenbaum went to his boarding house and stayed there. If he did——” The entrance, at that moment, of the young workman in whom Tom placed much confidence brought a sudden end to the talk. “You sent for me, Mr. Swift?” asked Clark, with a smile. “Is it about the new negative gravity machine I’m working on?”