Eighteen-year-old Ruby Santos, grappling with her mother's death and financial struggles, discovers her father's secret life as a magical underworld delivery person, leading her to take over his station and jump train lines, only to realize the perilous nature of the job and the dangerous world she has entered.

"Siku has always called the Zambezi River her home. She understands the water--and strangely enough, it seems to understand her, too, bending to her will and coming to her aid in times of need. But things are changing on the river--a great dam is being built, displacing thousands of Shonga people--and things are changing in Siku, too, as her ability to manipulate water grows out of control, and visions of a great serpent pull her further from reality...