In "Partials", Kira Walker is a sixteen-year-old medic as the story opens. She lives in a world in which there are only a few thousand humans left following a revolution in which a genetically-altered race of people left many humans dead and a plague killed millions more. In Kira's world, human babies are not able to survive more than a few hours before the plague kills them. The immunity the few remaining humans have is not passed on to their children and the humans have spent the years since the plague trying to find a cure. Kira believes she can figure out a cure and signs up to work in the maternity ward for that reason. However, she comes to realize no one is doing anything that will actually bring them closer to a cure.

There are few biological families remaining. Kira lives with an adopted "mother" named Nandita and several adopted "sisters." Kira remembers a man she believes is her father but has no memories of a mother before Nandita. She was only about five when the plague hit and knows most of what she accepts as fact from the teachings of the older survivors. She has been taught that the United States was in a war against China and a company called ParaGen created a genetically-altered race of humans as soldiers. They are known as the "Partials." Kira has also been taught that the Partials released the plague after they revolted against the humans.

Years have passed since the plague and Kira comes to believe the Partials may be able to provide the answers needed to create a cure so that infants can survive. Without a cure, the human race will soon die off altogether. Kira's desire to find a cure is increased when her adopted sister becomes pregnant. When she is denied official permission to travel into the Partials' territory in search of the data she needs, Kira sets out with a group of friends. There is a skirmish during the mission but Kira and the other survivors of the trip capture a Partial named Samm. Kira begins her experiments, this time with official sanction, and seems to be on the verge of a discovery when her laboratory is destroyed.

Kira uncovers a government plot that culminated in the destruction of the lab and plans to escape with Samm. This time she is captured by the Partial and discovers they have a medical emergency of their own. The Partials were engineered with a gene that causes them to die after about twenty years. She also discovers the Patrials have a cure for the plague and that they weren't the ones who released the virus, but that it was created by ParaGen. Finally, Kira learns that she is something other than human herself, though she has lived among the humans for as long as she can remember and has aged alongside the humans, unlike the other Partials.

Kira returns with the cure in time to save her adopted niece's life. The government is shaken by this turn of events and Kira knows she'll have to leave the city in order to find answers about herself. When she returns home, she discovers that Nandita is gone but there is a photo in Kira's room of a child with an adult couple. The woman in the photo is Nandita and Kira is the child. They are standing in front of a building with the words "ParaGen" on the front.