The Mystery of the Flying Express (Hardy Boys Mystery Stories Book 20)

iv, 217, [1] pp. 8vo. #20 in the Hardy Boys series. Light brown tweed boards, dark brown titles, orange Gretta endpapers, frontispiece by Paul Laune. "The Mystery Of The Flying Express is Volume 20 in the original Hardy Boys book series published by Grosset & Dunlap. The same title has been used for two completely unrelated story lines. The original story line involves the 'Flying Express' railway. This railway passes close to a foreign spy camp hidden in a forest. The revised edition involves a Flying Express hydrofoil." -- Wikipedia