It is the near future, and there have been amazing advances in genetics research. Through gene therapy, many deadly diseases (cancer, etc.) have been cured through these tests. The SimGen Corporation has created a transgenic species called SIMS, part chimpanzee and part human (Humanzee) and they are treated as slaves. Suddenly a group of sims working as caddies at a golf club want to unionize. They hire lawyer Patrick Sullivan to represent them, and he begins to ponder whether sims are entitled to human rights or not because they're part animal.
Patrick meets activist Romy Cadman and a mysterious man called Zero, who are on a crusade to destroy SimGen and stop the creation of sims. While the three of them try to protect the sims, they come close to uncovering a sinister secret in SimGen and the company will stop at nothing to stop the secret from getting out.
The story touches on a possible future for genetics research, including the idea of primate hybrids with human DNA, and asks the question: Where would such creatures stand in human society, and would they be considered animal or human?