Andre Norton 
Ralestone Luck 
With linked Table of Contents

The Ralestones were once a prestigious family, but now only three young Ralestones are left, all their money squandered by a guardian. They have only one hope: return to their old family plantation, Pirate’s Haven, and find the fabled sword, Ralestone’s Luck, which has guarded and brought prosperity to the Ralestones for centuries. But their old homestead seems to be haunted and the ghost doesn’t want them to find the blade.