Orphaned science nerd and maths prodigy Alice Valentine wants to ace her studies. She's spent all her life struggling to make friends, passed between foster families and care homes, isolated and lonely. Losing herself in academia from an early age, she becomes the first sixteen-year-old at her local university. Her whole world changes, but nothing can prepare Alice for the night she's attacked by a werewolf.

But even that isn't as strange as discovering she has an identical twin sister, Cassie.

And Cassie kills werewolves. And all the other monsters Alice didn't believe existed.

Alice and Cassie set off to discover what happened to their parents, a journey that takes them from northern England to the edge of the apocalypse, unsure if they will save the world or destroy it.