Time is running out. Cities are being engulfed in the Mist and humanity is on the brink of extinction. Theo believes he has found a way to stop mankind from Turning, but he doesn't know how to alter Cass's unique blood into a cure. Or if it can even be done.

Meanwhile, Cass struggles with the idea that she is possibly the savior of the world--a world she is not sure is worth saving.

From the Winchester manse to the steel city of Decadenn, there is something more chasing Cass than the House of Lords or the masked man who can walk in the Mist. Soon she must decide if she will use her blood to save mankind or let those who only care about themselves perish.