Boston: Houghton Mifflin, 1912. First edition. Hardcover. Near Fine / Near Fine. Original blue cloth with lettering in white to the front panel and spine. Stunning color design involving the frontispiece and title page as one canvas. Illustration on frontis page same as that of the jacket. Coles Phillips has designed this lovely image. With four full-page black and white plates by Harold J. Cue. Author's first book. A very intriguing story which begins with a basic question - What's going on behind the blue wall? An amazing copy of a very scarce early mystery in a superb dust jacket. Single leaf of ads to the rear and ads also on the flaps of the jacket and the rear panel. Listed in Hubin.