Circle of Death - The Shadow - Orson Welles & Agnes Moorehead

Who Knows What Evil Lurks in the Hearts of Men? ... The Shadow Knows!

On September 26, 1937, The Shadow radio drama, a new radio series 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 power to cloud men's minds so they cannot see him." In the magazine stories, The Shadow was not given the literal ability to become invisible.

The introduction from The Shadow radio program "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). At the end of each episode, The Shadow reminded listeners that "The weed of crime bears bitter fruit! Crime does not pay. The Shadow knows!" (Some early episodes, however, used the alternate statement, "As you sow evil, so shall you reap evil! Crime does not pay... The Shadow knows!")
Wikipedia

Originally Broadcast November 28, 1937