On the back of the unsightly excitement of Parasite, something like rigor sets in as the second half of what was a duology turns into the middle volume of a tolerance-testing trilogy. Symbiont isn’t a bad book by any means—it’s accessible, action-packed, and its premise remains appallingly plausible—but absent the ambiguity that made its predecessor so very unsettling, it’s lamentable for its length and lack of direction.
The first part of Parasitology chronicled the apocalyptic consequences of SymboGen’s latest and greatest innovation: the ubiquitous Intestinal Bodyguard—a magic pill meant to protect against allergy, illness and infection—was a worm which, in time, turned; a symbiotic organism supposed to support its host yet set, instead, on supplanting said. Before long, of course, this conflict of interests turned the population of San Francisco and its suburbs into zombies of a sort—sleepwalkers, as Mira Grant would have it.
The transition went differently for a few folks, though. After a catastrophic car crash, and at the cost of her every memory, Sally Mitchell’s parasite saved her life... or so she thought.