The Shadow - 1938/03/18 - The Silent Avenger

The Shadow is a collection of serialized dramas, originally in 1930s pulp novels and later in a variety of media. Its title character has been featured on the radio, in a long-running pulp magazine series, in American comic books, comic strips, television, serials, video games, and at least five feature films. The radio drama include episodes voiced by Orson Welles.

The Shadow, originally created to be a mysterious radio show narrator, was developed into a distinctive literary character in 1931 by writer Walter B. Gibson.

The Shadow debuted on July 31, 1930, as the mysterious narrator of the radio program Detective Story Hour, which was developed to boost sales of Street & Smith's monthly pulp Detective Story Magazine. When listeners of the program began asking at newsstands for copies of "that Shadow detective magazine", Street & Smith launched a magazine based on the character, and hired Gibson to create a concept to fit the name and voice and to write a story featuring him. The first issue of the pulp series The Shadow Magazine went on sale April 1, 1931.

On September 26, 1937, The Shadow, a new radio drama based on the character as created by Gibson for the pulp magazine, premiered with the story "The Death House Rescue", in which The Shadow was characterized as having "the hypnotic power to cloud men's minds so they cannot see him". In the magazine stories, The Shadow did not become literally invisible.

The introductory line from the radio adaptation of The Shadow – "Who knows what evil lurks in the hearts of men? The Shadow knows!" - spoken by actor Frank Readick, has earned a place in the American idiom. These words were accompanied by an ominous laugh and a musical theme, Camille Saint-Saëns' Le Rouet d'Omphale ("Omphale's Spinning Wheel," composed in 1872).

The Shadow, at the end of each episode, reminded listeners, "The weed of crime bears bitter fruit! Crime does not pay...The Shadow knows!"

Some early episodes used the alternate statement, "As you sow evil, so shall you reap evil! Crime does not pay...The Shadow knows!"
For more about The Shadow:
https://en.wikipedia.org/wiki/The_Shadow