What happens
Clark Kent, secretly Superman, works aboard Professor Thorpe's ship, the Juanita, after the professor's bathysphere comes under threat. Kent hears Morse code SOS tapping from below deck and descends with the professor to find a bound, blindfolded man held in a locked steel compartment. Kent frees him, and the rescued man reveals that the captain on the bridge is an impostor. Kent and the professor race back up to confront the men holding the ship. The episode is from The Adventures of Superman, an old-time radio series, and the original air date was August 28, 1940. The lead actors are not named in the transcript.
Aboard the ship Juanita at sea, in the Caribbean, with its hold, cabins, deck and radio cabin
Characters: Clark Kent, Professor Thorpe, Captain Maddox, Sparks, Wolf Cleveland, Escobar
Listen for: The Morse code SOS tapping from the hold, and the radio call from Escobar near the end
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.