Seventeen-year-old Jo McNair is one minute late for her curfew, and thanks to her controlling father, she's now locked out, cold and wandering the streets.

She has no money and nowhere to sleep. Halfway through the night she meets someone who says they're with a group working with at-risk kids, helping them get back on their feet. Jo gratefully accepts the offer of shelter for the night, only to find she has walked into a kidnapper's trap. Now Jo and several other teens are being held prisoner. Their captors drug them regularly and force them to donate their blood. What is so special about the teens' blood? And how long before they're drained dry? When one of the teens doesn't return, Jo suspects their days are numbered. She has to find a way to escape before their time runs out.