The story takes place in March of 2017, when Mayor Rich Rather and attorney Grant Griggs receive blackmail messages from a "Donna Dam," whose name they don't recognize. Donna Dam threatens to expose their shameful activities of forty years ago if the two men do not take a paternity test and if Mayor Rather does not withdraw his proposal to build a dam. The dam would create a lake on top of sacred Cherokee burial ground. Donna Dam demands $9,900 in cash to keep their secret. The editor of the local online newspaper Witherston on the Web, who publishes Donna Dam's letter to the editor, reports that forty years ago the Kelly Barnes Dam broke in Toccoa, Georgia, leaving thirty-nine people dead and many more homeless. What is the connection?
The teen-age twins Jaime and Jorge Arroyo, who helped solve the mysteries of Downstream and Fairfield's Auction, have just discovered an ancient Cherokee burial site when they hear an explosion upstream. The twin's mother, Detective Mev Arroyo, investigates the fire at the fishing shed, where Rather and Griggs had left their blackmail money, and discovers a body. DNA links the deceased to the twins' friend Eric.
As in the earlier Witherston murder mysteries Mev is aided in her sleuthing by Jaime and Jorge, her husband Paco, and her aunt Lottie, who help her learn the truth of what happened in 2017 and in 1977 and 1828. DNA ancestry tests reveal kinship between the Cherokees and the present inhabitants of the north Georgia town that no one would have predicted and some would not have disclosed.
The reader participates in the detection by getting information from many different sources: the characters' dialogue, email, text messages, deeds, and Witherston on the Web, which carries news reports, weather forecasts, announcements, obituaries, Jorge's column about nature, Jorge's cartoon, and Lottie's column about Witherston's history.