April Parker's plan for senior year is to tough it out with her overbearing stepfather for nine more months and move far away from home the second she graduates. It's what drives her to go through the motions every day and the reason his oppressive existence hasn't crushed her.

The last thing she expects is to end up inside a locked underground facility with dozens of other teenagers for company. As April attempts to unravel the mystery that brought them to the facility, she connects with a sweet southerner, a girl whose brightness is shadowed by the secrets she keeps, and an intuitive playboy whose interest in her discomforts her as much as it flatters her.

Making friends doesn't come easily to her, thanks to her stepfather, and she's forced to hide the stigma of her upbringing to keep herself safe in this new world. But when the stronger teenagers fight for control of the facility, April is left with two choices: to remain the insecure person she's always been, or to break free of Sam's chains and step forward as a leader, even if it means going up against the temperamental and compelling Marcus Fargo.

As conditions within the facility become more stressful and the teenagers' resilience is put to the test, strange things start to happen to them. Dangerous things. And if their kidnappers' silence is anything to go by, no one is coming to save them.