It's been fifteen years since the Medusa pandemic wiped out civilization, but the deadly virus continues to ravage the survivors - babies born to naturally immune mothers invariably die within days of their birth, calling into doubt the very survival of the human race.

And yet, hope persists.

Survivor Rachel Fisher, whose own past is tied to the origin of the apocalypse in fundamental and terrible ways, now carries with her a cache of precious vaccine that will protect newborns from the virus. For the first time in years, there is promise of a future for all of them.

But as Rachel struggles with deciding who will receive the shot, the danger is never far behind. A mysterious man from Rachel's past knows she has the vaccine.

His vision for the serum is darker than Rachel can possibly imagine, and he will stop at nothing to find it.

The thrilling conclusion to the IMMUNE series!