The Zombie Chronicles, Book 4: Poisonous Serum, Apocalypse Infection Unleashed (Volume 4) (Unabridged‪)‬

Three siblings fighting to survive in a zombie infested world... When they get caught in a flood during a rainstorm, the group is forced to take refuge. Soon, they are thrust into a mystery they can't explain, and when things slowly begin to unravel, they learn they have to play by a new set of rules...