Henry, Jessie, Benny, and Violet Alden meet Mike Wood and a strange chain of events begins. Mike's house is mysteriously burned down, a man in a blue hat appears, and the Aldens' uranium mine is in danger of being sabotaged.
Four orphaned children, afraid to go live with their grandfather, set up housekeeping in an abandoned boxcar and are doing fine until one of them becomes ill.
A friendly writer with a metal detector, the mysterious inhabitants of a tower house, and the discovery of a locket in the sand are ingredients for the Aldens' latest mystery.
