.27 is a number Ruby hates. It's a number that marks the percentage of the population that has survived. It's a number that means she's one of the "lucky" few still standing. And it's a number that says her father is probably dead. Against all odds, Ruby has survived the catastrophic onset of the killer rain. Two weeks after the radio started broadcasting the warning, "It's in the rain. It's fatal and there's no cure," the drinkable water is running out. Ruby's left with two options: persevere on her own or embark on a treacherous journey across the country to find her father—if he's even still alive. Don't miss the breathless conclusion to the H2O duology, .