The Footfalls Within is a Solomon Kane story in which Kane encounters a slave caravan after finding the body of a young woman killed by the slavers. Weird Tales accepted the story circa December 1930 and published it in September 1931. Howard received $56.

In a letter to Tevis Clyde Smith (letter #150), Howard wrote:

I recently sold a story to Weird Tales, a Solomon Kane story about which I hesitated several months before finally sending. It’s about the poorest story I’ve ever sold, marking a distinct transition in my development as a writer — a sort of half-way mark between pure action stuff and the cosmic horror tale, to which style I have at last managed to achieve, to a certain extent at least. I doubt if I will sell Weird Tales any of the latter very soon, because my style of handling this new theme is bound to be clumsy and amateurish, but I feel that I may eventually gain some recognition in that field. Of course, I’ll never equal Lovecraft, but I believe I can do at least as well as most of the other Weird Tale writers do in that line. Not that I mean to drop my action stuff, not in the least.

Howard later mentioned the story to H. P. Lovecraft in letter #173:

Yes, I did indeed like “The Whisperer in Darkness”, and appreciate the kind things you said about “The Footfalls Within”, which I feared failed miserably in creating the atmosphere I was striving after. I speak with full sincerity when I say I am bitterly disappointed that the Putnams rejected the mss. they were considering — disappointed not alone for your sake, but for the sake of literature as a whole.