The Mystery of the Flying Express
Frank and Joe Hardy are called to protect the maiden voyage of a new hydrofoil, the Flying Express, from saboteurs. When the vessel vanishes and a key operative disappears, the teen detectives find themselves in a dangerous pursuit. They must outwit a criminal gang known as the Zodiac to solve the mystery and recover the stolen hydrofoil.
This book is the twentieth installment in the long-running Hardy Boys Mystery Stories series. While each book presents a self-contained mystery, reading them in publication order allows for a more complete experience of the characters' development and recurring elements.
The story was adapted into a segment for The Hardy Boys/Nancy Drew Mysteries television series in 1977, starring Parker Stevenson and Shaun Cassidy as Frank and Joe Hardy. The television version takes some liberties with the original plot and characters.
The Mystery of the Flying Express is notable for its early use of advanced technology, featuring a hydrofoil as a central plot device, which was quite futuristic for its publication era. It also introduces a memorable criminal organization, the Zodiac, which adds a layer of recurring challenge for the Hardy Boys.