“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 Deathhouse Rescue,” in which The Shadow was characterized as having “the power to cloud men’s minds so they cannot see him.” As in the magazine stories, The Shadow was not given the literal ability to become invisible.”
Go to The Shadow Old Time Radio Show OTR Broadcast, 39 01 08 Island of the Devil for the description.