“I don’t mind going back and going through my stunt again, even for the fifty-first performance,” offered Ned, with enthusiasm. “I don’t care how late it is. Helen won’t expect me now.” “Did you have an engagement?” asked Tom, looking sharply at his friend. “And I kept you here doing a song and dance act half the night when Helen expected you! That’s too bad! If I’d known——” “Keep your hair on!” chuckled Ned. “I didn’t _really_ have a date with Helen. I said I might drop around if there wasn’t anything to do here. But she knows you well enough to make allowances for emergency work—and this was just that.” “Yes, it is an emergency all right,” returned Tom slowly. “But I shall give it up for the night. No use keeping you any longer, Ned. Go on home and I’ll try it again to-morrow with a different wave length. I think that’s where the difficulty is. We’ll tackle it again in the morning.” “All right,” assented Ned Newton, and he could not keep out of his voice a little note of satisfaction and relief. Truth to tell, he was a bit tired. For several weeks now he had been helping Tom Swift on the latter’s newest idea—an invention, Tom declared, that would be the greatest on record and one that would tend to revolutionize the radio and moving picture industries. This was a daring plan Tom had conceived of making a radio machine, both sending and receiving, that would enable a person or any number of persons not only to hear a distant performance in their own home, but also see those taking part. “I’ll make it possible,” declared Tom Swift, “for a man to sit in his easy chair, smoking a cigar in his library, and, by a turn of a switch, not only to hear the latest opera but also to see each and every performer and witness the whole play.” When Ned had asked how the vision would appear to the man, Tom had replied: “On an electrified screen attached to his radio receiver by which he listens to the songs and music.” As Tom said, the problem of transmitting an entire opera through the air was simple enough. That had been done many times. So had the transmitting of photographs by wireless. Also, in a limited way, television had made it possible for a person in a dark room to be visible to lookers-on in another apartment some distance away. “But I am going to combine the two!” declared Tom Swift. “I want to make it possible for a synchronized performance of seeing and hearing to take place. Thus when a theater is equipped with my sending apparatus and I have perfected my receiver, one need never go outside the house to enjoy a theatrical performance or a concert.”