This novel of speculative fiction tells the story of a young woman's struggle for a sense of self, and for freedom, following the grafting of her identity into the body and mind of a chimpanzee. As Eva struggles to integrate who she was with who she has become, the narrative also explores themes relating to the nature of the relationship between humanity and nature, and the cruelty of scientific experimentation on animals.

The first part of the novel is titled "Waking." Slowly, after a long period of unconsciousness, eleven year old Eva wakes, first for minutes at a time and then for longer and longer periods. Comforted and reassured by her mother, Eva nevertheless experiences increasing unease as she develops the strong sense that in some fundamental way, she is not the person she was. Eventually she catches sight of herself in a mirror, and discovers that her mind is now inside the body of a chimpanzee. As she struggles to find the right way to move, to eat, to think and to communicate, Eva also struggles to find an accepting balance between her own identity and that of the chimpanzee whose mind hers has displaced.

In the second part of the novel, entitled "Living," word begins to spread into the outside world not only of what Eva experienced, but how successfully she has recovered and how happily she is living a new integrated life. All is not as happy as it seems, however, since the press is being fed idealized news stories by the corporation that controls both Eva and the research that gave her a new life, and Eva and her family are having increasingly challenging struggles dealing with what she has become. Among these struggles is Eva's growing awareness of the cruelties being perpetrated on other chimpanzees in the research facility, awareness heightened when she discovers that two other attempts to perform similar integrative surgeries have failed.

Around this time, Eva makes both a choice to help her scientist father in his research into the lives and ways of chimpanzees, and a discovery. This occurs when she meets Grog, a young man determined to free chimpanzees, like those with whom Eva spends time as the result of her efforts to help her father, from what he sees as the controlling, damaging corporate and scientific ethos that, in Grog's opinion, views the animals as essentially worthless. Eva, more determined to establish a closer relationship with her father through helping him in his research, initially resists Grog's pleas for her to help him in his mission. Eventually, though, circumstances lead her to realize that Grog is right, and together they formulate a plan that will enable Eva to lead her chimp companions back into the wild.

Eva and Grog put their plan into action when Eva's father takes her and the other chimps to a tropical island to conduct observational experiments on their behavior. A sudden typhoon disrupts his plans, but enables Eva to fulfill hers. Under the cover of damaging weather, she leads a small group of other chimps to an area of the island where they cannot be seen, heard, or otherwise watched. Eventually, however, Eva and the others are tracked down, not only by Grog and Eva's father, but also by both the corporation that owns the rights to Eva and other corporations eager to exploit her flight to freedom as well as the growing animal rights movement triggered by coverage of that flight, for profit. Eva, angered by what she perceives to be betrayal and exploitation all around her, fights for her continued freedom, and eventually wins.

The book's brief third section, "Dying," is set twenty years after the events of the previous section. The elderly Eva, near death following a series of strokes, is visited by a pair of friendly human beings who describe for her the troubled condition of the outside world. After they go, Eva is taken by other chimps including her daughter to a private, quiet place to die. There, Eva imagines what life will be like for the generations after generations that will follow her, now that their evolutionary path has been affected by her human influence.