This book was intended for the young adult market, though it wasn’t called that back then. Published in 1965, it was written by the great Walter Gibson, a novelette with illustrations by a I. H. Guyer. The publisher was Wonder Books.
That style so familiar to Shadow fans is there and my only problem with it was the length, forty-eight pages in magazine periodical size. Everything seemed rushed and not developed enough. I think a medium length novel would have done the plot more justice.

Napoleon and Illya are in New Orleans are in New Orleans to meet contacts about some new organization called IMP. Both are murdered before hand though and a coin found on one is the only clue. A distinquished looking bust of a man with the words El Diablo over the top and IMP under.

El Diablo is an old legend of a ruler in the Caribbean Islands a hundred years ago. Napoleon leaves to investigate, only to disappear enroute, contact cut off. Illya is sent after to find him and continue the mission.

For such a short work, it has a voodoo queen, a big castle, THRUSH working around the edges, a megalomaniac looking like some Emperor from the past, a giant torturer. As I said, to much packed into such a short piece.

Still, as an U.N.C.L.E. fan, I enjyed a story by Walter Gibson.