What happens
Captain Bradford, Joan, Mrs. Gregory, Jerry and Tex are trapped on the artificial island of Euclidea, where a man named G-47 rules a colony in silence. When an alarm sounds, the island men go out to hunt an escaping man. Bradford uses seaweed cloth, which blocks sound, light and rays, to hide from the island's monitoring, and he tries to send a radio message for help. Hanson, the engineer, is seen signaling from the yacht. Bradford learns that a staged escape was meant to cover his radio attempt, and Tex and Pat hear the news of the escapee's fate. Jerry is still missing at the end of the episode.
The artificial island of Euclidea, with its cloth factory, piers, submarine locks, and the Gregory yacht.
Characters: Captain Bradford, Joan, Mrs. Gregory, Jerry, Tex, Hanson, G-47, Pat
Listen for: The silence of the island contrasted with the alarms, and the radio exchange between Bradford and Johnson.
Written from the episode itself; it never gives away the ending. Every recording is remastered for the stream: cleaned of rumble, hiss and mains hum (and the old TV whine where we found it), then levelled in two passes to steady broadcast loudness, so one show is never quieter than the next.