Three years ago, after a terrible fight with her father, Lydia Bradshaw vanished without a trace.

Her younger sister Gwen never gives up hope, though, waiting for Lydia to eventually come home.

But when Lydia finally does resurface, it's not what Gwen expected. Lydia's changed in her time away, in ways Gwen can barely understand. After her family home burns, Gwen gets taken in by a cadre of vampire hunters who call themselves Project Fifteen. They welcome Gwen, teaching her how to hunt and fight vampires. And Gwen embraces the opportunity to take revenge on the vampires who have hurt her family.

But not everyone is what they seem. Everyone has secrets, even Gwen. Will Gwen be able to survive her introduction into the hidden world of Project Fifteen?