In the year 241, twelve-year-old Lina trades jobs on Assignment Day to be a Messenger to run to new places in her decaying but beloved city, perhaps even to glimpse Unknown Regions.
Lina and Doon are thrilled to see their people join them above ground in the vibrant village of Sparks, but suspicion and prejudice soon turn the villagers and newcomers against each other.
Squirrel, a stray puppy, tells her life story, from her nurturing mother and brother to making her own way in the world, facing busy highways, changing seasons, and humans both gentle and brutal.