John D. Swain (1870-1952) was a prolific pulp author, playwright, novelist, poet, essayist, and movie script writer. He won the O. Henry Memorial Award in 1931.

His story 'The Man Who Knew Too Much' is a fantastic tale originally published inBlack Mask magazine. Although it became known as the home of hardboiled mystery writers, in its early yearsBlack Mask published all manner of tales, including this one, which-had in been written in later years-would have been at home in eitherWeird Tales orAmazing Stories.

Includes an introduction by John Betancourt.