Frank and Joe Hardy drive to the to see the new Bayport Airport. Before even getting there the boys are almost run over by an airplane flown by the airmail pilot Giles Ducroy. As a result of the event, Ducroy loses his job, blames the boys, and then frames them for a mail robbery. Although the boys don’t have an alibi they are bailed out of jail by Mr. Applegate (from The Tower Treasure) and Mr. Jefferson (from The Mystery of Cabin Island). The Hardy boys overhear Ducroy and two other criminals planning a major robbery. The boys find out that Ducroy and company bought an airplane. In order to keep up with the gang they decide to stow in the back of the airplane. Ducroy and company make a daring and dangerous attempt to steal a major payroll from the airmail plane. The Hardy boys manage to capture the thieves with the help of the targeted pilot. He ends up using the crooks’ plane to deliver his cargo. The boys are vindicated when they bring in the real mail robbers, plus having averted a major robbery.

Much has changed in America since 1930. The modern listener may be delighted with the warmth and innocence of the characters, but uncomfortable with the racial, social, and sexist terms and stereotypes. As such, this book is a part of our heritage, a window into our real past.