On the evening of Horseshoe Bay's annual Harvest Carnival, a whole new mystery unfolds for Nancy when the body of a mysterious young man is discovered on the Hudson carnival grounds. The Drew Crew is drawn into the case by a host of confounding clues surrounding a new menace terrorizing the town - a killer who has an enigmatic connection to none other than Nancy's newest foil: Temperance Hudson. 

On the trail of the Frozen Hearts Killer, Nancy and her friends follow a surprising lead from a podcaster at an annual convention for amateur sleuths - where they also find themselves unraveling ghostly clues about a homicide from the 1950s.