The Mystery of the Spiral Bridge is the forty-fifth volume in the original The Hardy Boys series of mystery books for children and teens published by Grosset & Dunlap.
This book was written for the Stratemeyer Syndicate by Andrew E. Svenson in 1966.
The Hardy Boys track down the saboteurs who kidnapped their father, and have to keep them from blowing up a bridge near Boontown, Kentucky. The bridge is being built by Tony Prito's father's construction company. Mr Hardy is ill for most of the story. The villains are mostly ex-crooks who want that area of the bridge for themselves.