Professor James Houghland, after years of research, has perfected revolutionary improvements in television, but he refuses all offers from companies that want to buy his inventions, and several unscrupulous promoters plan to get them by other means. On the night of the first public demonstration of his inventions, several well-known television experts are at Houghland's home. The first broadcast is an unqualified success. As the second broadcast is about to begin Houghland falls dead, and the police headed by Chief Nelson arrive, and no one is permitted to leave the house. Several of the guests are suspected: Arthur Perry, Hougland's assistant, because he was out of the room when the lights were turned on after the murder; Donald Jordan, because he tried to bribe Perry to steal the secret; Richard Grayson, an ambitious, young television engineer, because he had promised to secure the secret for his company, and Dr. Henry Scofield, because he refuses to explain a mysterious telephone call that he made shortly before the murder.