The Mystery Of The Flying Express, The Hardy Boys Mystery Stories. Author: Franklin W. Dixon. 217 pages. Hardcover book, no dust jacket. Publisher: Grosset & Dunlap,  copyright 1941, first printing 1941.

Condition: The book is in very good condition. The covers have some very light wear along the edges. The binding is very good and there are no loose or torn pages. The interior pages are in very good condition with no writing, marks, or creases. No dust jacket (see photos).

1941 printing info: the 1941 printing used a tan/brown cloth cover with dark lettering (Format III, used for Hardy Boys books from 1932-1943). The orange silhouette end papers included the artist's "gretta" signature on the lower left of the left page. 

In the 1941 printing, the Hardy Boys mother was mistakenly referred to as "Mildred" rather than "Laura". On page 4, Aunt Gertrude says "Haven't seen your mother. M-i-l-d-r-e-d!".  This error was corrected in later versions.

Synopsis: In The Mystery of the Flying Express, Frank and Joe Hardy become involved in one of their father Fenton Hardy’s most intriguing cases when a mysterious stranger is discovered secretly listening to conversations in the Hardy home. The boys soon uncover evidence pointing to a foreign spy organization operating within the United States. Their investigation takes them far from Bayport, as they follow a trail of coded messages, suspicious travelers, and other clues connected with the fast passenger train known as the “Flying Express.”

As Frank and Joe pursue the conspirators by train, airplane, automobile, and on foot, they gradually discover that the Flying Express is being used to transport secret messages and operatives to a hidden training camp in the West. Danger increases as the boys infiltrate the spy network and attempt to uncover its ultimate plans. The original 1941 story is a particularly action-oriented Hardy Boys adventure, combining mystery, espionage, coded communications, travel, and the brothers' characteristic determination to bring the criminals to justice.