A decade in the future, humanity thrives in the absence of sickness and disease. We owe our good health to a humble parasite - a genetically engineered tapeworm developed by the pioneering SymboGen Corporation. When implanted, the tapeworm protects us from illness, boosts our immune system - even secretes designer drugs. It's been successful beyond the scientists' wildest dreams. Now, years on, almost every human being has a SymboGen tapeworm living within them. But these parasites are getting restless. They want their own lives...and will do anything to get them.

THE SECOND BOOK IN MIRA GRANT'S TERRIFYING PARASITOLOGY SERIES. THE ENEMY IS INSIDE US. The SymboGen designed tapeworms were created to relieve humanity of disease and sickness. But the implants in the majority of the world's population began attacking their hosts turning them into a ravenous horde. Now those who do not appear to be afflicted are being gathered for quarantine as panic spreads, but Sal and her companions must discover how the tapeworms are taking over their hosts, what their eventual goal is, and how they can be stopped.

The final book in Mira Grant's terrifying Parasitology trilogy. The outbreak has spread, tearing apart the foundations of society, as implanted tapeworms have turned their human hosts into a seemingly mindless mob. Sal and her family are trapped between bad and worse, and must find a way to compromise between the two sides of their nature before the battle becomes large enough to destroy humanity, and everything that humanity has built...including the chimera. The broken doors are closing. Can Sal make it home?