Hypatia is a companion child, a cyborg with the consciousness of a child, designed to help her non-verbal human sister, Alexandra, navigate the world. When a flash knocks out the power and a civil war erupts, the sisters are forced to travel through powerless cities and dangerous country roads in search of refuge on the eastern coast of the United States. Realizing that without access to a charging station it's only a matter of time before her battery fails, Hypatia must deliver Alexandra to safety before it's too late. Yet, as Hypatia and Alexandra encounter other companion children that have gone berserk, Hypatia begins to suspect the flash may have done more than just take out the power. Can Alexandra trust her sister, and is Hypatia exactly what she seems?