The 49th issue of the Sanctum Books reprint of The Shadow holds a curious little treasure. Rounding out the issue, which contains The Shadow Laughs and Voice of Death, is an anonymous memo found in Lester Dent’s archives. Entitled “The Shadow’s Invisible Cloak,” the memo seeks a naturalistic explanation for The Shadow’s ability to turn invisible, a carryover into the pulps from the radio show.

At one page, the memo develops some serious chemistry as to the odd properties of The Shadow’s cloak before diving into various strengths and weaknesses of the technique. Sprinkled throughout the memo is a constant reminder that just because a man might come across such a cloak, he would need to know how it was made in order to reproduce it. This provided both a warning as to the complexity of the chemical processes used and a convenient excuse if Walter Gibson changed his mind about the manufacture. The refrain also provides a clue as to the identity of the memo’s writer.

Such a refrain appeared many times in the pages of Astounding, in the words of its celebrated editor, John W. Campbell. Not only was the style similar, but Campbell was also an MIT-trained physicist with a background in the physics and industrial chemistry needed to create such a conjecture. And Campbell had mulled over the idea of an invisibility cloak before, in his own stories “Out of Night” and its sequel “Cloak of Aesir.” Thanks to his friendship with Gibson, Campbell ended up as the unofficial science advisor for not only The Shadow but many of the other hero pulps under John Nanovic’s tenure as editor.

However, it was in 1944 when a Street & Smith editor forwarded “The Shadow’s Invisibility Cloak” to Lester Dent. It is unknown whether William de Grouchey, Babette Rosemund, or the nameless female sub-editor who actually oversaw both The Shadow and Doc Savage was responsible. But the contents inspired the Doc Savage novel “Death Had Yellow Eyes”. It also may have inspired an October 1944 issue of Shadow Comics which contained the first-ever meeting between The Shadow and Doc Savage. The two would team up again in the comics, but it wouldn’t be until 2015’s The Sinister Shadow before the Knight of Darkness and the Man of Bronze crossed paths in the novels.

All because editors are fans, too.