Entrapment can cause insanity, but it can also forge something else entirely.

Nineteen-year-old Harper has been trapped in a secret underground facility-a combination of a military school, a ward, and a laboratory-for the last five years. Memories of her prior life are gone, she's forced to train for combat, and after being condemned as an experimental test subject, an electrifying power begins to rise within her.

Harper finally escapes, but not all of her friends get out. Unsure if she'll be able to remember who she is or control her new power, she must find and save her friends from the clutches of the man who incarcerated her before they fall too far into his operations-and before she's captured again.

With the help of a mysterious, fiercely protective-and handsome-police officer and a crew of determined allies, Harper fights to figure out who's behind the Vault and to get justice. But the more she learns, the more she begins to realize there's more to the story, and her background, than she had ever dreamed possible...

What would you do if your most dangerous weapon was also your worst nightmare?