What happens
Jerry Hall and Joan Gregory, prisoners of the underwater city of Euclydia, enter a vast cavern and find a small radio-controlled airplane flying alone. They meet Octavo, an old scientist who experiments with musical notes, and ask him what he is doing. He explains that he is searching for the keynote that will destroy the plane's motor. The young visitors watch as he tests notes against the flying model, and the demonstration proves frightening. Jerry and Joan are left unsettled by what the notes can do, and the episode of Magic Island is part of the series.
The underwater city of Euclydia, inside a huge natural cavern beneath the sea
Characters: Jerry Hall, Joan Gregory, Octavo, Salise
Listen for: Octavo's musical glasses and the sound of the small plane's motor as he searches for the note that will destroy it
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.