Franklin W. Dixon 
The Tower Treasure 

In The Tower Treasure, teenage detectives Frank and Joe Hardy tackle their first case. After a robbery leaves the Tower Mansion stripped of valuable treasures, the boys embark on a thrilling adventure to clear the name of a family friend. Mystery and danger await as they unearth hidden secrets and confront unexpected challenges.
Note: this is the original 1927 version of the story, which was rewritten — and toned down — in the 1950s. We believe this is the superior story.