Nephthys Kinwell is a taxi driver of sorts in Washington, DC, ferrying passengers in a 1967 Plymouth Belvedere with a ghost in the trunk. Endless rides and alcohol help her manage her grief over the death of her twin brother, Osiris, who was murdered and dumped in the Anacostia River. Unknown to Nephthys when the novel opens in 1977, her great-nephew, ten-year-old Dash, is drawn to the banks of that very same river. It is there that Dash has conversations with a mysterious figure he calls the "River Man." When Dash arrives unexpectedly at Nephthys's door bearing a cryptic note about his conversations with the River Man, Nephthys must face what frightens her most.