When I finished writing The Ehrengraf Defense in 1976, I knew I had found a character I’d like to revisit. But it was Frederic Dannay’s immediate enthusiasm for Ehrengraf that made me write one story after another about the diminutive attorney. Fred, of course, was one of the pair of cousins who wrote the Ellery Queen mysteries, and it was Fred who edited Ellery Queen’s Mystery Magazine, and he...