The mystery begins on a snowy winter afternoon when thirteen-year-old Renfro Horn notices old Captain Pete Hall behaving suspiciously with game birds out of season. While walking past the sprawling, supposedly abandoned Hall estate, Renfro spots unexplained lights flashing through the windows, sparking a personal investigation that runs parallel to his responsibilities as an Evening Globe newspaper carrier. To secure unrestricted access to the neighborhood without raising parental suspicion, Renfro cleverly acquires a difficult local paper route known as Old Grief. As Renfro delivers papers through biting cold and snow, he builds his subscriber base and wins a turkey contest, all while gathering clues about a mysterious heavy-set stranger who frequently watches Judge Wier's house.
The plot thickens dramatically when Judge Wier's twelve-year-old daughter Helen is abducted from her home without a sound, triggering a massive police search and casting a shadow of fear over the community. Renfro discovers a vital clue left behind by the prowler: a man's eyebrows accidentally frozen and torn off against a frosted windowpane during the stakeout. Teaming up with the family's romantic and imaginative Scottish maid, Mary Dugan, Renfro hides the eyebrows and resolves to solve the abduction before the bumbling city detectives.
Their path leads them from the eerie, abandoned Hall mansion and its underground counterfeiting cave to Twin Cedar Cabin during a Boy Scout overnight hike, where weird electrical battery-operated lights and mysterious footprints confound the campers. Renfro's relentless sleuthing eventually leads him straight into a trap, where he is ambushed and imprisoned inside a limestone cave beneath the Hall property. There, he discovers that the kidnper is an ex-convict named Bart, seeking vicious revenge against Judge Wier who sentenced him to fifteen years behind bars. Locked in the subterranean cell, Renfro manages to communicate through the wall with Helen Wier, who is held captive nearby.
With the help of a friendly Airedale dog named Lang Tammy, Renfro breaks free from his bonds, escapes the cavern, and rushes to the newspaper office. Backed by the Globe's editors, a rescue party descends on the cave, frees Helen, and restores peace to the town. Renfro returns triumphant to his family, having earned the profound respect of his parents, the local police, and his newspaper manager, proving his mettle as a brilliant young investigator.
