What happens
Brick Reed, publisher of the Daily Sentinel, and his valet Kato, both secretly working as the Green Hornet, investigate a murder on a city-bound train. Ken Benson, a suspect in the killing, is linked to a mathematician, Dr. Gorky, who has a secretary named Marietta. Clues include a timetable and an envelope both marked with the same pattern of joined triangles. Reed and Kato search Dr. Gorky's house and leave the Hornet seal on his desk, which alarms the doctor's group. The Hornet confronts the doctor in his study while his associates wait in hiding.
A city in the United States, including a Pullman train, a newspaper office, a secluded house and a study
Characters: Brick Reed, Kato, Mike Axford, Dr. Gorky, Marietta, Ken Benson, Mark, Leon
Listen for: The doodled triangle marks linking the envelope and the timetable, and the confrontation in Dr. Gorky's study
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.