Genetically engineered tapeworms that protect most of the human populace from illness, boost everyone's immune system, and even secrete designer drugs begin to change and want out of human bodies they occupy.

"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 earth has been invaded by a species that take over the minds of their human hosts while leaving their bodies intact, and most of humanity has succumbed. But Melanie Stryder refuses to fade away. Wanderer, the invading "soul" who has been given Melanie's body, knew about the challenges of living inside a human: the overwhelming emotions, the too vivid memories. But there was one difficulty Wanderer didn't expect: the former tenant of her body refusing...